diff --git a/src/accounting/static/js/summary-helper.js b/src/accounting/static/js/summary-helper.js
new file mode 100644
index 0000000..0f8d91d
--- /dev/null
+++ b/src/accounting/static/js/summary-helper.js
@@ -0,0 +1,531 @@
+/* The Mia! Accounting Flask Project
+ * summary-helper.js: The JavaScript for the summary helper
+ */
+
+/*  Copyright (c) 2023 imacat.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+/* Author: imacat@mail.imacat.idv.tw (imacat)
+ * First written: 2023/2/28
+ */
+
+// Initializes the page JavaScript.
+document.addEventListener("DOMContentLoaded", function () {
+    SummaryHelper.initialize();
+});
+
+/**
+ * A summary helper.
+ *
+ */
+class SummaryHelper {
+
+    /**
+     * The entry type
+     * @type {string}
+     */
+    #entryType;
+
+    /**
+     * The prefix of the HTML ID and class
+     * @type {string}
+     */
+    #prefix;
+
+    /**
+     * The default tab ID
+     * @type {string}
+     */
+    #defaultTabId;
+
+    /**
+     * Constructs a summary helper.
+     *
+     * @param form {HTMLFormElement} the summary helper form
+     */
+    constructor(form) {
+        this.#entryType = form.dataset.entryType;
+        this.#prefix = "accounting-summary-helper-" + form.dataset.entryType;
+        this.#defaultTabId = form.dataset.defaultTabId;
+        this.#init();
+    }
+
+    /**
+     * Initializes the summary helper.
+     *
+     */
+    #init() {
+        const helper = this;
+        const tabs = Array.from(document.getElementsByClassName(this.#prefix + "-tab"));
+        tabs.forEach(function (tab) {
+            tab.onclick = function () {
+                helper.#switchToTab(tab.dataset.tabId);
+            }
+        });
+        this.#initializeGeneralTagHelper();
+        this.#initializeGeneralTripHelper();
+        this.#initializeBusTripHelper();
+        this.#initializeNumberHelper();
+        this.#initializeSubmission();
+    }
+
+    /**
+     * Switches to a tab.
+     *
+     * @param tabId {string} the tab ID.
+     */
+    #switchToTab(tabId) {
+        const tabs = Array.from(document.getElementsByClassName(this.#prefix + "-tab"));
+        const pages = Array.from(document.getElementsByClassName(this.#prefix + "-page"));
+        tabs.forEach(function (tab) {
+            if (tab.dataset.tabId === tabId) {
+                tab.classList.add("active");
+                tab.ariaCurrent = "page";
+            } else {
+                tab.classList.remove("active");
+                tab.ariaCurrent = "false";
+            }
+        });
+        pages.forEach(function (page) {
+            if (page.dataset.tabId === tabId) {
+                page.classList.remove("d-none");
+                page.ariaCurrent = "page";
+            } else {
+                page.classList.add("d-none");
+                page.ariaCurrent = "false";
+            }
+        });
+    }
+
+    /**
+     * Initializes the general tag helper.
+     *
+     */
+    #initializeGeneralTagHelper() {
+        const buttons = Array.from(document.getElementsByClassName(this.#prefix + "-general-btn-tag"));
+        const summary = document.getElementById(this.#prefix + "-summary");
+        const tag = document.getElementById(this.#prefix + "-general-tag");
+        const updateSummary = function () {
+            const pos = summary.value.indexOf("—");
+            const prefix = tag.value === ""? "": tag.value + "—";
+            if (pos === -1) {
+                summary.value = prefix + summary.value;
+            } else {
+                summary.value = prefix + summary.value.substring(pos + 1);
+            }
+        }
+        buttons.forEach(function (button) {
+            button.onclick = function () {
+                buttons.forEach(function (otherButton) {
+                    otherButton.classList.remove("btn-primary");
+                    otherButton.classList.add("btn-outline-primary");
+                });
+                button.classList.remove("btn-outline-primary");
+                button.classList.add("btn-primary");
+                tag.value = button.dataset.value;
+                updateSummary();
+            };
+        });
+        tag.onchange = function () {
+            buttons.forEach(function (button) {
+                if (button.dataset.value === tag.value) {
+                    button.classList.remove("btn-outline-primary");
+                    button.classList.add("btn-primary");
+                } else {
+                    button.classList.remove("btn-primary");
+                    button.classList.add("btn-outline-primary");
+                }
+            });
+            updateSummary();
+        };
+    }
+
+    /**
+     * Initializes the general trip helper.
+     *
+     */
+    #initializeGeneralTripHelper() {
+        const buttons = Array.from(document.getElementsByClassName(this.#prefix + "-travel-btn-tag"));
+        const summary = document.getElementById(this.#prefix + "-summary");
+        const tag = document.getElementById(this.#prefix + "-travel-tag");
+        const from = document.getElementById(this.#prefix + "-travel-from");
+        const directionButtons = Array.from(document.getElementsByClassName(this.#prefix + "-travel-direction"))
+        const to = document.getElementById(this.#prefix + "-travel-to");
+        const updateSummary = function () {
+            let direction;
+            for (const button of directionButtons) {
+                if (button.classList.contains("btn-primary")) {
+                    direction = button.dataset.arrow;
+                    break;
+                }
+            }
+            summary.value = tag.value + "—" + from.value + direction + to.value;
+        };
+        buttons.forEach(function (button) {
+            button.onclick = function () {
+                buttons.forEach(function (otherButton) {
+                    otherButton.classList.remove("btn-primary");
+                    otherButton.classList.add("btn-outline-primary");
+                });
+                button.classList.remove("btn-outline-primary");
+                button.classList.add("btn-primary");
+                tag.value = button.dataset.value;
+                updateSummary();
+            };
+        });
+        tag.onchange = function () {
+            buttons.forEach(function (button) {
+                if (button.dataset.value === tag.value) {
+                    button.classList.remove("btn-outline-primary");
+                    button.classList.add("btn-primary");
+                } else {
+                    button.classList.remove("btn-primary");
+                    button.classList.add("btn-outline-primary");
+                }
+            });
+            updateSummary();
+        };
+        from.onchange = updateSummary;
+        directionButtons.forEach(function (button) {
+            button.onclick = function () {
+                directionButtons.forEach(function (otherButton) {
+                    otherButton.classList.remove("btn-primary");
+                    otherButton.classList.add("btn-outline-primary");
+                });
+                button.classList.remove("btn-outline-primary");
+                button.classList.add("btn-primary");
+                updateSummary();
+            };
+        });
+        to.onchange = updateSummary;
+    }
+
+    /**
+     * Initializes the bus trip helper.
+     *
+     */
+    #initializeBusTripHelper() {
+        const buttons = Array.from(document.getElementsByClassName(this.#prefix + "-bus-btn-tag"));
+        const summary = document.getElementById(this.#prefix + "-summary");
+        const tag = document.getElementById(this.#prefix + "-bus-tag");
+        const route = document.getElementById(this.#prefix + "-bus-route");
+        const from = document.getElementById(this.#prefix + "-bus-from");
+        const to = document.getElementById(this.#prefix + "-bus-to");
+        const updateSummary = function () {
+            summary.value = tag.value + "—" + route.value + "—" + from.value + "→" + to.value;
+        };
+        buttons.forEach(function (button) {
+            button.onclick = function () {
+                buttons.forEach(function (otherButton) {
+                    otherButton.classList.remove("btn-primary");
+                    otherButton.classList.add("btn-outline-primary");
+                });
+                button.classList.remove("btn-outline-primary");
+                button.classList.add("btn-primary");
+                tag.value = button.dataset.value;
+                updateSummary();
+            };
+        });
+        tag.onchange = function () {
+            buttons.forEach(function (button) {
+                if (button.dataset.value === tag.value) {
+                    button.classList.remove("btn-outline-primary");
+                    button.classList.add("btn-primary");
+                } else {
+                    button.classList.remove("btn-primary");
+                    button.classList.add("btn-outline-primary");
+                }
+            });
+            updateSummary();
+        };
+        route.onchange = updateSummary;
+        from.onchange = updateSummary;
+        to.onchange = updateSummary;
+    }
+
+    /**
+     * Initializes the number helper.
+     *
+     */
+    #initializeNumberHelper() {
+        const summary = document.getElementById(this.#prefix + "-summary");
+        const number = document.getElementById(this.#prefix + "-number");
+        number.onchange = function () {
+            const found = summary.value.match(/^(.+)×(\d+)$/);
+            if (found !== null) {
+                summary.value = found[1];
+            }
+            if (number.value > 1) {
+                summary.value = summary.value + "×" + String(number.value);
+            }
+        };
+    }
+
+    /**
+     * Initializes the summary submission
+     *
+     */
+    #initializeSubmission() {
+        const form = document.getElementById(this.#prefix);
+        const helper = this;
+        form.onsubmit = function () {
+            if (helper.#validate()) {
+                helper.#submit();
+            }
+            return false;
+        };
+    }
+
+    /**
+     * Validates the form.
+     *
+     * @return {boolean} true if valid, or false otherwise
+     */
+    #validate() {
+        return true;
+    }
+
+    /**
+     * Submits the summary.
+     *
+     */
+    #submit() {
+        const summary = document.getElementById(this.#prefix + "-summary");
+        const formSummaryControl = document.getElementById("accounting-entry-form-summary-control");
+        const formSummary = document.getElementById("accounting-entry-form-summary");
+        const helperModal = document.getElementById(this.#prefix + "-modal");
+        const entryModal = document.getElementById("accounting-entry-form-modal");
+        if (summary.value === "") {
+            formSummaryControl.classList.remove("accounting-not-empty");
+        } else {
+            formSummaryControl.classList.add("accounting-not-empty");
+        }
+        formSummary.dataset.value = summary.value;
+        formSummary.innerText = summary.value;
+        bootstrap.Modal.getInstance(helperModal).hide();
+        bootstrap.Modal.getOrCreateInstance(entryModal).show();
+    }
+
+    /**
+     * Initializes the summary help when it is shown.
+     *
+     * @param isNew {boolean} true for adding a new journal entry, or false otherwise
+     */
+    initShow(isNew) {
+        const closeButtons = Array.from(document.getElementsByClassName(this.#prefix + "-close"));
+        closeButtons.forEach(function (button) {
+            if (isNew) {
+                button.dataset.bsTarget = "";
+            } else {
+                button.dataset.bsTarget = "#accounting-entry-form-modal";
+            }
+        });
+        this.#reset();
+        if (!isNew) {
+            this.#populate();
+        }
+    }
+
+    /**
+     * Resets the summary helper.
+     *
+     */
+    #reset() {
+        const inputs = Array.from(document.getElementsByClassName(this.#prefix + "-input"));
+        const tagButtons = Array.from(document.getElementsByClassName(this.#prefix + "-btn-tag"));
+        const directionButtons = Array.from(document.getElementsByClassName(this.#prefix + "-travel-direction"));
+        inputs.forEach(function (input) {
+            input.value = "";
+            input.classList.remove("is-invalid");
+        });
+        tagButtons.forEach(function (btnTag) {
+            btnTag.classList.remove("btn-primary");
+            btnTag.classList.add("btn-outline-primary");
+        });
+        directionButtons.forEach(function (btnDirection) {
+            if (btnDirection.classList.contains("accounting-default")) {
+                btnDirection.classList.remove("btn-outline-primary");
+                btnDirection.classList.add("btn-primary");
+            } else {
+                btnDirection.classList.add("btn-outline-primary");
+                btnDirection.classList.remove("btn-primary");
+            }
+        });
+        this.#switchToTab(this.#defaultTabId);
+    }
+
+    /**
+     * Populates the summary helper from the journal entry form.
+     *
+     */
+    #populate() {
+        const formSummary = document.getElementById("accounting-entry-form-summary");
+        const summary = document.getElementById(this.#prefix + "-summary");
+        summary.value = formSummary.dataset.value;
+        const pos = summary.value.indexOf("—");
+        if (pos === -1) {
+            return;
+        }
+        let found;
+        found = summary.value.match(/^(.+?)—(.+?)—(.+?)→(.+?)(?:×(\d+)?)?$/);
+        if (found !== null) {
+            return this.#populateBusTrip(found[1], found[2], found[3], found[4], found[5]);
+        }
+        found = summary.value.match(/^(.+?)—(.+?)([→↔])(.+?)(?:×(\d+)?)?$/);
+        if (found !== null) {
+            return this.#populateGeneralTrip(found[1], found[2], found[3], found[4], found[5]);
+        }
+        found = summary.value.match(/^(.+?)—.+?(?:×(\d+)?)?$/);
+        if (found !== null) {
+            return this.#populateGeneralTag(found[1], found[2]);
+        }
+    }
+
+    /**
+     * Populates a bus trip.
+     *
+     * @param tagName {string} the tag name
+     * @param routeName {string} the route name or route number
+     * @param fromName {string} the name of the origin
+     * @param toName {string} the name of the destination
+     * @param numberStr {string|undefined} the number of items, if any
+     */
+    #populateBusTrip(tagName, routeName, fromName, toName, numberStr) {
+        const tag = document.getElementById(this.#prefix + "-bus-tag");
+        const route = document.getElementById(this.#prefix + "-bus-route");
+        const from = document.getElementById(this.#prefix + "-bus-from");
+        const to = document.getElementById(this.#prefix + "-bus-to");
+        const number = document.getElementById(this.#prefix + "-number");
+        const buttons = Array.from(document.getElementsByClassName(this.#prefix + "-bus-btn-tag"));
+        tag.value = tagName;
+        route.value = routeName;
+        from.value = fromName;
+        to.value = toName;
+        if (numberStr !== undefined) {
+            number.value = parseInt(numberStr);
+        }
+        buttons.forEach(function (button) {
+            if (button.dataset.value === tagName) {
+                button.classList.remove("btn-outline-primary");
+                button.classList.add("btn-primary");
+            }
+        });
+        this.#switchToTab("bus");
+    }
+
+    /**
+     * Populates a general trip.
+     *
+     * @param tagName {string} the tag name
+     * @param fromName {string} the name of the origin
+     * @param direction {string} the direction arrow, either "→" or "↔"
+     * @param toName {string} the name of the destination
+     * @param numberStr {string|undefined} the number of items, if any
+     */
+    #populateGeneralTrip(tagName, fromName, direction, toName, numberStr) {
+        const tag = document.getElementById(this.#prefix + "-travel-tag");
+        const from = document.getElementById(this.#prefix + "-travel-from");
+        const to = document.getElementById(this.#prefix + "-travel-to");
+        const number = document.getElementById(this.#prefix + "-number");
+        const buttons = Array.from(document.getElementsByClassName(this.#prefix + "-travel-btn-tag"));
+        const directionButtons = Array.from(document.getElementsByClassName(this.#prefix + "-travel-direction"));
+        tag.value = tagName;
+        from.value = fromName;
+        directionButtons.forEach(function (btnDirection) {
+            if (btnDirection.dataset.arrow === direction) {
+                btnDirection.classList.remove("btn-outline-primary");
+                btnDirection.classList.add("btn-primary");
+            } else {
+                btnDirection.classList.add("btn-outline-primary");
+                btnDirection.classList.remove("btn-primary");
+            }
+        });
+        to.value = toName;
+        if (numberStr !== undefined) {
+            number.value = parseInt(numberStr);
+        }
+        buttons.forEach(function (button) {
+            if (button.dataset.value === tagName) {
+                button.classList.remove("btn-outline-primary");
+                button.classList.add("btn-primary");
+            }
+        });
+        this.#switchToTab("travel");
+    }
+
+    /**
+     * Populates a general tag.
+     *
+     * @param tagName {string} the tag name
+     * @param numberStr {string|undefined} the number of items, if any
+     */
+    #populateGeneralTag(tagName, numberStr) {
+        const tag = document.getElementById(this.#prefix + "-general-tag");
+        const number = document.getElementById(this.#prefix + "-number");
+        const buttons = Array.from(document.getElementsByClassName(this.#prefix + "-general-btn-tag"));
+        tag.value = tagName;
+        if (numberStr !== undefined) {
+            number.value = parseInt(numberStr);
+        }
+        buttons.forEach(function (button) {
+            if (button.dataset.value === tagName) {
+                button.classList.remove("btn-outline-primary");
+                button.classList.add("btn-primary");
+            }
+        });
+        this.#switchToTab("general");
+    }
+
+    /**
+     * The summary helpers.
+     * @type {{debit: SummaryHelper, credit: SummaryHelper}}
+     */
+    static #helpers = {}
+
+    /**
+     * Initializes the summary helpers.
+     *
+     */
+    static initialize() {
+        const forms = Array.from(document.getElementsByClassName("accounting-summary-helper"));
+        for (const form of forms) {
+            const helper = new SummaryHelper(form);
+            this.#helpers[helper.#entryType] = helper;
+        }
+        this.#initializeTransactionForm();
+    }
+
+    /**
+     * Initializes the transaction form.
+     *
+     */
+    static #initializeTransactionForm() {
+        const entryForm = document.getElementById("accounting-entry-form");
+        const formSummaryControl = document.getElementById("accounting-entry-form-summary-control");
+        const helpers = this.#helpers;
+        formSummaryControl.onclick = function () {
+            helpers[entryForm.dataset.entryType].initShow(false);
+        };
+    }
+
+    /**
+     * Initializes the summary helper for a new journal entry.
+     *
+     * @param entryType {string} the entry type, either "debit" or "credit"
+     */
+    static initializeNewJournalEntry(entryType) {
+        this.#helpers[entryType].initShow(true);
+    }
+}
diff --git a/src/accounting/static/js/transaction-form.js b/src/accounting/static/js/transaction-form.js
index 5bc183e..539266e 100644
--- a/src/accounting/static/js/transaction-form.js
+++ b/src/accounting/static/js/transaction-form.js
@@ -157,6 +157,7 @@ function initializeNewEntryButton(button) {
     const formAccountControl = document.getElementById("accounting-entry-form-account-control");
     const formAccount = document.getElementById("accounting-entry-form-account");
     const formAccountError = document.getElementById("accounting-entry-form-account-error")
+    const formSummaryControl = document.getElementById("accounting-entry-form-summary-control");
     const formSummary = document.getElementById("accounting-entry-form-summary");
     const formSummaryError = document.getElementById("accounting-entry-form-summary-error");
     const formAmount = document.getElementById("accounting-entry-form-amount");
@@ -165,19 +166,23 @@ function initializeNewEntryButton(button) {
         entryForm.dataset.currencyIndex = button.dataset.currencyIndex;
         entryForm.dataset.entryType = button.dataset.entryType;
         entryForm.dataset.entryIndex = button.dataset.entryIndex;
-        formAccountControl.classList.remove("accounting-not-empty")
+        formAccountControl.classList.remove("accounting-not-empty");
         formAccountControl.classList.remove("is-invalid");
         formAccountControl.dataset.bsTarget = button.dataset.accountModal;
         formAccount.innerText = "";
         formAccount.dataset.code = "";
         formAccount.dataset.text = "";
         formAccountError.innerText = "";
-        formSummary.value = "";
-        formSummary.classList.remove("is-invalid");
+        formSummaryControl.dataset.bsTarget = "#accounting-summary-helper-" + button.dataset.entryType + "-modal";
+        formSummaryControl.classList.remove("accounting-not-empty");
+        formSummaryControl.classList.remove("is-invalid");
+        formSummary.dataset.value = "";
+        formSummary.innerText = ""
         formSummaryError.innerText = ""
         formAmount.value = "";
         formAmount.classList.remove("is-invalid");
         formAmountError.innerText = "";
+        SummaryHelper.initializeNewJournalEntry(button.dataset.entryType);
     };
 }
 
@@ -209,6 +214,7 @@ function initializeJournalEntry(entry) {
     const control = document.getElementById(entry.dataset.prefix + "-control");
     const formAccountControl = document.getElementById("accounting-entry-form-account-control");
     const formAccount = document.getElementById("accounting-entry-form-account");
+    const formSummaryControl = document.getElementById("accounting-entry-form-summary-control");
     const formSummary = document.getElementById("accounting-entry-form-summary");
     const formAmount = document.getElementById("accounting-entry-form-amount");
     control.onclick = function () {
@@ -224,7 +230,14 @@ function initializeJournalEntry(entry) {
         formAccount.innerText = accountCode.dataset.text;
         formAccount.dataset.code = accountCode.value;
         formAccount.dataset.text = accountCode.dataset.text;
-        formSummary.value = summary.value;
+        formSummaryControl.dataset.bsTarget = "#accounting-summary-helper-" + entry.dataset.entryType + "-modal";
+        if (summary.value === "") {
+            formSummaryControl.classList.remove("accounting-not-empty");
+        } else {
+            formSummaryControl.classList.add("accounting-not-empty");
+        }
+        formSummary.dataset.value = summary.value;
+        formSummary.innerText = summary.value;
         formAmount.value = amount.value;
         validateJournalEntryForm();
     };
@@ -239,7 +252,6 @@ function initializeJournalEntryFormModal() {
     const entryForm = document.getElementById("accounting-entry-form");
     const formAccountControl = document.getElementById("accounting-entry-form-account-control");
     const formAccount = document.getElementById("accounting-entry-form-account");
-    const formSummary = document.getElementById("accounting-entry-form-summary");
     const formAmount = document.getElementById("accounting-entry-form-amount");
     const modal = document.getElementById("accounting-entry-form-modal");
     formAccountControl.onclick = function () {
@@ -268,7 +280,6 @@ function initializeJournalEntryFormModal() {
             btnClear.disabled = false;
         }
     };
-    formSummary.onchange = validateJournalEntrySummary;
     formAmount.onchange = validateJournalEntryAmount;
     entryForm.onsubmit = function () {
         if (validateJournalEntryForm()) {
@@ -320,10 +331,9 @@ function validateJournalEntryAccount() {
  * @private
  */
 function validateJournalEntrySummary() {
-    const field = document.getElementById("accounting-entry-form-summary");
+    const control = document.getElementById("accounting-entry-form-summary-control");
     const error = document.getElementById("accounting-entry-form-summary-error");
-    field.value = field.value.trim();
-    field.classList.remove("is-invalid");
+    control.classList.remove("is-invalid");
     error.innerText = "";
     return true;
 }
@@ -393,8 +403,8 @@ function saveJournalEntryForm() {
     accountCode.value = formAccount.dataset.code;
     accountCode.dataset.text = formAccount.dataset.text;
     accountText.innerText = formAccount.dataset.text;
-    summary.value = formSummary.value;
-    summaryText.innerText = formSummary.value;
+    summary.value = formSummary.dataset.value;
+    summaryText.innerText = formSummary.dataset.value;
     amount.value = formAmount.value;
     amountText.innerText = formatDecimal(new Decimal(formAmount.value));
     if (entryForm.dataset.entryIndex === "new") {
diff --git a/src/accounting/templates/accounting/transaction/expense/include/form-currency-item.html b/src/accounting/templates/accounting/transaction/expense/include/form-currency-item.html
index 543360b..400e6ba 100644
--- a/src/accounting/templates/accounting/transaction/expense/include/form-currency-item.html
+++ b/src/accounting/templates/accounting/transaction/expense/include/form-currency-item.html
@@ -70,7 +70,7 @@ First written: 2023/2/25
         </div>
 
         <div>
-          <button class="btn btn-primary accounting-btn-new-entry accounting-currency-{{ currency_index }}-btn-new-entry" type="button" data-currency-index="{{ currency_index }}" data-entry-type="debit" data-entry-index="new" data-account-modal="#accounting-debit-account-selector-modal" data-bs-toggle="modal" data-bs-target="#accounting-entry-form-modal">
+          <button class="btn btn-primary accounting-btn-new-entry accounting-currency-{{ currency_index }}-btn-new-entry" type="button" data-currency-index="{{ currency_index }}" data-entry-type="debit" data-entry-index="new" data-account-modal="#accounting-debit-account-selector-modal" data-bs-toggle="modal" data-bs-target="#accounting-summary-helper-debit-modal">
             <i class="fas fa-plus"></i>
             {{ A_("New") }}
           </button>
diff --git a/src/accounting/templates/accounting/transaction/include/entry-form-modal.html b/src/accounting/templates/accounting/transaction/include/entry-form-modal.html
index 32fc5e3..0dc44d2 100644
--- a/src/accounting/templates/accounting/transaction/include/entry-form-modal.html
+++ b/src/accounting/templates/accounting/transaction/include/entry-form-modal.html
@@ -36,9 +36,11 @@ First written: 2023/2/25
             <div id="accounting-entry-form-account-error" class="invalid-feedback"></div>
           </div>
 
-          <div class="form-floating mb-3">
-            <input id="accounting-entry-form-summary" class="form-control" type="text" value="" placeholder=" ">
-            <label for="accounting-entry-form-summary">{{ A_("Summary") }}</label>
+          <div class="mb-3">
+            <div id="accounting-entry-form-summary-control" class="form-control accounting-clickable accounting-material-text-field" data-bs-toggle="modal" data-bs-target="">
+              <label class="form-label" for="accounting-entry-form-summary">{{ A_("Summary") }}</label>
+              <div id="accounting-entry-form-summary" data-value=""></div>
+            </div>
             <div id="accounting-entry-form-summary-error" class="invalid-feedback"></div>
           </div>
 
diff --git a/src/accounting/templates/accounting/transaction/include/form.html b/src/accounting/templates/accounting/transaction/include/form.html
index c09ac1b..f25fd9c 100644
--- a/src/accounting/templates/accounting/transaction/include/form.html
+++ b/src/accounting/templates/accounting/transaction/include/form.html
@@ -24,6 +24,7 @@ First written: 2023/2/26
 {% block accounting_scripts %}
   <script src="{{ url_for("accounting.static", filename="js/drag-and-drop-reorder.js") }}"></script>
   <script src="{{ url_for("accounting.static", filename="js/transaction-form.js") }}"></script>
+  <script src="{{ url_for("accounting.static", filename="js/summary-helper.js") }}"></script>
 {% endblock %}
 
 {% block content %}
@@ -85,6 +86,9 @@ First written: 2023/2/26
 </form>
 
 {% include "accounting/transaction/include/entry-form-modal.html" %}
+{% for summary_helper in form.summary_helper.types %}
+  {% include "accounting/transaction/include/summary-helper-modal.html" %}
+{% endfor %}
 {% block account_selector_modals %}{% endblock %}
 
 {% endblock %}
diff --git a/src/accounting/templates/accounting/transaction/include/summary-helper-modal.html b/src/accounting/templates/accounting/transaction/include/summary-helper-modal.html
new file mode 100644
index 0000000..0eb20db
--- /dev/null
+++ b/src/accounting/templates/accounting/transaction/include/summary-helper-modal.html
@@ -0,0 +1,171 @@
+{#
+The Mia! Accounting Flask Project
+entry-form-modal.html: The modal of the summary helper
+
+ Copyright (c) 2023 imacat.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+
+Author: imacat@mail.imacat.idv.tw (imacat)
+First written: 2023/2/28
+#}
+<form id="accounting-summary-helper-{{ summary_helper.type }}" class="accounting-summary-helper" data-entry-type="{{ summary_helper.type }}" data-default-tab-id="general">
+  <div id="accounting-summary-helper-{{ summary_helper.type }}-modal" class="modal fade" tabindex="-1" aria-labelledby="accounting-summary-helper-{{ summary_helper.type }}-modal-label" aria-hidden="true">
+    <div class="modal-dialog">
+      <div class="modal-content">
+        <div class="modal-header">
+          <h1 class="modal-title fs-5" id="accounting-summary-helper-{{ summary_helper.type }}-modal-label">
+            <label for="accounting-summary-helper-{{ summary_helper.type }}-summary">{{ A_("Summary") }}</label>
+          </h1>
+          <button type="button" class="btn-close accounting-summary-helper-{{ summary_helper.type }}-close" data-bs-toggle="modal" data-bs-target="" aria-label="{{ A_("Close") }}"></button>
+        </div>
+        <div class="modal-body">
+          <div class="mb-3">
+            <input id="accounting-summary-helper-{{ summary_helper.type }}-summary" class="form-control accounting-summary-helper-{{ summary_helper.type }}-input" type="text" aria-labelledby="accounting-summary-helper-{{ summary_helper.type }}-modal-label">
+          </div>
+          <ul class="nav nav-tabs mb-2">
+            <li class="nav-item">
+              <span class="nav-link active accounting-clickable accounting-summary-helper-{{ summary_helper.type }}-tab" aria-current="page" data-tab-id="general">
+                {{ A_("General") }}
+              </span>
+            </li>
+            <li class="nav-item">
+              <span class="nav-link accounting-clickable accounting-summary-helper-{{ summary_helper.type }}-tab" aria-current="false" data-tab-id="travel">
+                {{ A_("Travel") }}
+              </span>
+            </li>
+            <li class="nav-item">
+              <span class="nav-link accounting-clickable accounting-summary-helper-{{ summary_helper.type }}-tab" aria-current="false" data-tab-id="bus">
+                {{ A_("Bus") }}
+              </span>
+            </li>
+            <li class="nav-item">
+              <span class="nav-link accounting-clickable accounting-summary-helper-{{ summary_helper.type }}-tab" aria-current="false" data-tab-id="regular">
+                {{ A_("Regular") }}
+              </span>
+            </li>
+            <li class="nav-item">
+              <span class="nav-link accounting-clickable accounting-summary-helper-{{ summary_helper.type }}-tab" aria-current="false" data-tab-id="number">
+                {{ A_("Number") }}
+              </span>
+            </li>
+          </ul>
+          {# A general summary with a tag #}
+          <div class="accounting-summary-helper-{{ summary_helper.type }}-page" aria-current="page" data-tab-id="general">
+            <div class="form-floating mb-2">
+              <input id="accounting-summary-helper-{{ summary_helper.type }}-general-tag" class="form-control accounting-summary-helper-{{ summary_helper.type }}-input" type="text" value="" placeholder=" ">
+              <label class="form-label" for="accounting-summary-helper-{{ summary_helper.type }}-general-tag">{{ A_("Tag") }}</label>
+            </div>
+
+            <div>
+              {% for tag in summary_helper.general.tags %}
+                <button class="btn btn-outline-primary accounting-summary-helper-{{ summary_helper.type }}-btn-tag accounting-summary-helper-{{ summary_helper.type }}-general-btn-tag" type="button" tabindex="-1" data-value="{{ tag.name }}">
+                  {{ tag }}
+                </button>
+              {% endfor %}
+            </div>
+          </div>
+
+          {# A general trip with the origin and distination #}
+          <div class="accounting-summary-helper-{{ summary_helper.type }}-page d-none" aria-current="false" data-tab-id="travel">
+            <div class="form-floating mb-2">
+              <input id="accounting-summary-helper-{{ summary_helper.type }}-travel-tag" class="form-control accounting-summary-helper-{{ summary_helper.type }}-input" type="text" value="" placeholder=" ">
+              <label class="form-label" for="accounting-summary-helper-{{ summary_helper.type }}-travel-tag">{{ A_("Tag") }}</label>
+              <div id="accounting-summary-helper-{{ summary_helper.type }}-travel-tag-error" class="invalid-feedback"></div>
+            </div>
+
+            <div>
+              {% for tag in summary_helper.travel.tags %}
+                <button class="btn btn-outline-primary accounting-summary-helper-{{ summary_helper.type }}-btn-tag accounting-summary-helper-{{ summary_helper.type }}-travel-btn-tag" type="button" tabindex="-1" data-value="{{ tag.name }}">
+                  {{ tag }}
+                </button>
+              {% endfor %}
+            </div>
+
+            <div class="d-flex justify-content-between mt-2">
+              <div class="form-floating">
+                <input id="accounting-summary-helper-{{ summary_helper.type }}-travel-from" class="form-control accounting-summary-helper-{{ summary_helper.type }}-input" type="text" value="" placeholder=" ">
+                <label class="form-label" for="accounting-summary-helper-{{ summary_helper.type }}-travel-from">{{ A_("From") }}</label>
+                <div id="accounting-summary-helper-{{ summary_helper.type }}-travel-from-error" class="invalid-feedback"></div>
+              </div>
+              <div class="btn-group-vertical ms-1 me-1">
+                <button class="btn btn-primary accounting-summary-helper-{{ summary_helper.type }}-travel-direction accounting-default" type="button" data-arrow="&rarr;">&rarr;</button>
+                <button class="btn btn-outline-primary accounting-summary-helper-{{ summary_helper.type }}-travel-direction" type="button" data-arrow="&harr;">&harr;</button>
+              </div>
+              <div class="form-floating">
+                <input id="accounting-summary-helper-{{ summary_helper.type }}-travel-to" class="form-control accounting-summary-helper-{{ summary_helper.type }}-input" type="text" value="" placeholder=" ">
+                <label class="form-label" for="accounting-summary-helper-{{ summary_helper.type }}-travel-to">{{ A_("To") }}</label>
+                <div id="accounting-summary-helper-{{ summary_helper.type }}-travel-to-error" class="invalid-feedback"></div>
+              </div>
+            </div>
+          </div>
+
+          {# A bus trip with the route name or route number, the origin and distination #}
+          <div class="accounting-summary-helper-{{ summary_helper.type }}-page d-none" aria-current="false" data-tab-id="bus">
+            <div class="d-flex justify-content-between mb-2">
+              <div class="form-floating me-2">
+                <input id="accounting-summary-helper-{{ summary_helper.type }}-bus-tag" class="form-control accounting-summary-helper-{{ summary_helper.type }}-input" type="text" value="" placeholder=" ">
+                <label class="form-label" for="accounting-summary-helper-{{ summary_helper.type }}-bus-tag">{{ A_("Tag") }}</label>
+                <div id="accounting-summary-helper-{{ summary_helper.type }}-bus-tag-error" class="invalid-feedback"></div>
+              </div>
+              <div class="form-floating">
+                <input id="accounting-summary-helper-{{ summary_helper.type }}-bus-route" class="form-control accounting-summary-helper-{{ summary_helper.type }}-input" type="text" value="" placeholder=" ">
+                <label class="form-label" for="accounting-summary-helper-{{ summary_helper.type }}-bus-route">{{ A_("Route") }}</label>
+                <div id="accounting-summary-helper-{{ summary_helper.type }}-bus-route-error" class="invalid-feedback"></div>
+              </div>
+            </div>
+
+            <div>
+              {% for tag in summary_helper.bus.tags %}
+                <button class="btn btn-outline-primary accounting-summary-helper-{{ summary_helper.type }}-btn-tag accounting-summary-helper-{{ summary_helper.type }}-bus-btn-tag" type="button" tabindex="-1" data-value="{{ tag.name }}">
+                  {{ tag }}
+                </button>
+              {% endfor %}
+            </div>
+
+            <div class="d-flex justify-content-between mt-2">
+              <div class="form-floating me-2">
+                <input id="accounting-summary-helper-{{ summary_helper.type }}-bus-from" class="form-control accounting-summary-helper-{{ summary_helper.type }}-input" type="text" value="" placeholder=" ">
+                <label class="form-label" for="accounting-summary-helper-{{ summary_helper.type }}-bus-from">{{ A_("From") }}</label>
+                <div id="accounting-summary-helper-{{ summary_helper.type }}-bus-from-error" class="invalid-feedback"></div>
+              </div>
+              <div class="form-floating">
+                <input id="accounting-summary-helper-{{ summary_helper.type }}-bus-to" class="form-control accounting-summary-helper-{{ summary_helper.type }}-input" type="text" value="" placeholder=" ">
+                <label class="form-label" for="accounting-summary-helper-{{ summary_helper.type }}-bus-to">{{ A_("To") }}</label>
+                <div id="accounting-summary-helper-{{ summary_helper.type }}-bus-to-error" class="invalid-feedback"></div>
+              </div>
+            </div>
+          </div>
+
+          {# A regular income/payment #}
+          <div class="accounting-summary-helper-{{ summary_helper.type }}-page d-none" aria-current="false" data-tab-id="regular">
+            {# TODO: To be done #}
+          </div>
+
+          {# The number of items #}
+          <div class="accounting-summary-helper-{{ summary_helper.type }}-page d-none" aria-current="false" data-tab-id="number">
+            <div class="form-floating">
+              <input id="accounting-summary-helper-{{ summary_helper.type }}-number" class="form-control accounting-summary-helper-{{ summary_helper.type }}-input" type="number" min="1" value="" placeholder=" ">
+              <label class="form-label" for="accounting-summary-helper-{{ summary_helper.type }}-number">{{ A_("The number of items") }}</label>
+              <div id="accounting-summary-helper-{{ summary_helper.type }}-number-error" class="invalid-feedback"></div>
+            </div>
+          </div>
+        </div>
+        <div class="modal-footer">
+          <button type="button" class="btn btn-secondary accounting-summary-helper-{{ summary_helper.type }}-close" data-bs-toggle="modal" data-bs-target="">{{ A_("Cancel") }}</button>
+          <button id="accounting-summary-helper-{{ summary_helper.type }}-btn-save" type="submit" class="btn btn-primary">{{ A_("Save") }}</button>
+        </div>
+      </div>
+    </div>
+  </div>
+</form>
diff --git a/src/accounting/templates/accounting/transaction/income/include/form-currency-item.html b/src/accounting/templates/accounting/transaction/income/include/form-currency-item.html
index 9569007..6e35e69 100644
--- a/src/accounting/templates/accounting/transaction/income/include/form-currency-item.html
+++ b/src/accounting/templates/accounting/transaction/income/include/form-currency-item.html
@@ -70,7 +70,7 @@ First written: 2023/2/25
         </div>
 
         <div>
-          <button class="btn btn-primary accounting-btn-new-entry accounting-currency-{{ currency_index }}-btn-new-entry" type="button" data-currency-index="{{ currency_index }}" data-entry-type="credit" data-entry-index="new" data-account-modal="#accounting-credit-account-selector-modal" data-bs-toggle="modal" data-bs-target="#accounting-entry-form-modal">
+          <button class="btn btn-primary accounting-btn-new-entry accounting-currency-{{ currency_index }}-btn-new-entry" type="button" data-currency-index="{{ currency_index }}" data-entry-type="credit" data-entry-index="new" data-account-modal="#accounting-credit-account-selector-modal" data-bs-toggle="modal" data-bs-target="#accounting-summary-helper-credit-modal">
             <i class="fas fa-plus"></i>
             {{ A_("New") }}
           </button>
diff --git a/src/accounting/templates/accounting/transaction/transfer/include/form-currency-item.html b/src/accounting/templates/accounting/transaction/transfer/include/form-currency-item.html
index 6ea3e40..3ccd592 100644
--- a/src/accounting/templates/accounting/transaction/transfer/include/form-currency-item.html
+++ b/src/accounting/templates/accounting/transaction/transfer/include/form-currency-item.html
@@ -72,7 +72,7 @@ First written: 2023/2/25
           </div>
 
           <div>
-            <button class="btn btn-primary accounting-btn-new-entry accounting-currency-{{ currency_index }}-btn-new-entry" type="button" data-currency-index="{{ currency_index }}" data-entry-type="debit" data-entry-index="new" data-account-modal="#accounting-debit-account-selector-modal" data-bs-toggle="modal" data-bs-target="#accounting-entry-form-modal">
+            <button class="btn btn-primary accounting-btn-new-entry accounting-currency-{{ currency_index }}-btn-new-entry" type="button" data-currency-index="{{ currency_index }}" data-entry-type="debit" data-entry-index="new" data-account-modal="#accounting-debit-account-selector-modal" data-bs-toggle="modal" data-bs-target="#accounting-summary-helper-debit-modal">
               <i class="fas fa-plus"></i>
               {{ A_("New") }}
             </button>
@@ -112,7 +112,7 @@ First written: 2023/2/25
           </div>
 
           <div>
-            <button class="btn btn-primary accounting-btn-new-entry accounting-currency-{{ currency_index }}-btn-new-entry" type="button" data-currency-index="{{ currency_index }}" data-entry-type="credit" data-entry-index="new" data-account-modal="#accounting-credit-account-selector-modal" data-bs-toggle="modal" data-bs-target="#accounting-entry-form-modal">
+            <button class="btn btn-primary accounting-btn-new-entry accounting-currency-{{ currency_index }}-btn-new-entry" type="button" data-currency-index="{{ currency_index }}" data-entry-type="credit" data-entry-index="new" data-account-modal="#accounting-credit-account-selector-modal" data-bs-toggle="modal" data-bs-target="#accounting-summary-helper-credit-modal">
               <i class="fas fa-plus"></i>
               {{ A_("New") }}
             </button>
diff --git a/src/accounting/transaction/forms.py b/src/accounting/transaction/forms.py
index 20610c9..5faafea 100644
--- a/src/accounting/transaction/forms.py
+++ b/src/accounting/transaction/forms.py
@@ -364,6 +364,14 @@ class TransactionForm(FlaskForm):
         return [x for x in self.currencies.errors
                 if isinstance(x, str) or isinstance(x, LazyString)]
 
+    @property
+    def summary_helper(self) -> SummaryHelper:
+        """Returns the summary helper.
+
+        :return: The summary helper.
+        """
+        return SummaryHelper()
+
 
 T = t.TypeVar("T", bound=TransactionForm)
 """A transaction form variant."""
diff --git a/src/accounting/transaction/summary_helper.py b/src/accounting/transaction/summary_helper.py
new file mode 100644
index 0000000..7fe2695
--- /dev/null
+++ b/src/accounting/transaction/summary_helper.py
@@ -0,0 +1,227 @@
+# The Mia! Accounting Flask Project.
+# Author: imacat@mail.imacat.idv.tw (imacat), 2023/2/27
+
+#  Copyright (c) 2023 imacat.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+"""The summary helper.
+
+"""
+import typing as t
+
+import sqlalchemy as sa
+
+from accounting import db
+from accounting.models import Account, JournalEntry
+
+
+class SummaryAccount:
+    """An account for a summary tag."""
+
+    def __init__(self, account: Account, freq: int):
+        """Constructs an account for a summary tag.
+
+        :param account: The account.
+        :param freq: The frequency of the tag with the account.
+        """
+        self.__account: Account = account
+        """The account."""
+        self.code: str = account.code
+        """The account code."""
+        self.freq: int = freq
+        """The frequency of the tag with the account."""
+
+    def __str__(self) -> str:
+        """Returns the string representation of the account.
+
+        :return: The string representation of the account.
+        """
+        return str(self.__account)
+
+    def add_freq(self, freq: int) -> None:
+        """Adds the frequency of an account.
+
+        :param freq: The frequency of the tag name with the account.
+        :return: None.
+        """
+        self.freq = self.freq + freq
+
+
+class SummaryTag:
+    """A summary tag."""
+
+    def __init__(self, name: str):
+        """Constructs a summary tag.
+
+        :param name: The tag name.
+        """
+        self.name: str = name
+        """The tag name."""
+        self.__account_dict: dict[int, SummaryAccount] = {}
+        """The accounts that come with the tag, in the order of their
+        frequency."""
+        self.freq: int = 0
+        """The frequency of the tag."""
+
+    def __str__(self) -> str:
+        """Returns the string representation of the tag.
+
+        :return: The string representation of the tag.
+        """
+        return self.name
+
+    def add_account(self, account: Account, freq: int):
+        """Adds an account.
+
+        :param account: The associated account.
+        :param freq: The frequency of the tag name with the account.
+        :return: None.
+        """
+        self.__account_dict[account.id] = SummaryAccount(account, freq)
+        self.freq = self.freq + freq
+
+    @property
+    def accounts(self) -> list[SummaryAccount]:
+        """Returns the accounts by the order of their frequencies.
+
+        :return: The accounts by the order of their frequencies.
+        """
+        return sorted(self.__account_dict.values(), key=lambda x: -x.freq)
+
+
+class SummaryType:
+    """A summary type"""
+
+    def __init__(self, type_id: t.Literal["general", "travel", "bus"]):
+        """Constructs a summary type.
+
+        :param type_id: The type ID, either "general", "travel", or "bus".
+        """
+        self.id: t.Literal["general", "travel", "bus"] = type_id
+        """The type ID."""
+        self.__tag_dict: dict[str, SummaryTag] = {}
+        """A dictionary from the tag name to their corresponding tag."""
+
+    def add_tag(self, name: str, account: Account, freq: int) -> None:
+        """Adds a tag.
+
+        :param name: The tag name.
+        :param account: The associated account.
+        :param freq: The frequency of the tag name with the account.
+        :return: None.
+        """
+        if name not in self.__tag_dict:
+            self.__tag_dict[name] = SummaryTag(name)
+        self.__tag_dict[name].add_account(account, freq)
+
+    @property
+    def tags(self) -> list[SummaryTag]:
+        """Returns the tags by the order of their frequencies.
+
+        :return: The tags by the order of their frequencies.
+        """
+        return sorted(self.__tag_dict.values(), key=lambda x: -x.freq)
+
+
+class SummaryEntryType:
+    """A summary type"""
+
+    def __init__(self, entry_type_id: t.Literal["debit", "credit"]):
+        """Constructs a summary entry type.
+
+        :param entry_type_id: The entry type ID, either "debit" or "credit".
+        """
+        self.type: t.Literal["debit", "credit"] = entry_type_id
+        """The entry type."""
+        self.general: SummaryType = SummaryType("general")
+        """The general tags."""
+        self.travel: SummaryType = SummaryType("travel")
+        """The travel tags."""
+        self.bus: SummaryType = SummaryType("bus")
+        """The bus tags."""
+        self.__type_dict: dict[t.Literal["general", "travel", "bus"],
+                               SummaryType] \
+            = {x.id: x for x in {self.general, self.travel, self.bus}}
+        """A dictionary from the type ID to the corresponding tags."""
+
+    def add_tag(self, tag_type: t.Literal["general", "travel", "bus"],
+                name: str, account: Account, freq: int) -> None:
+        """Adds a tag.
+
+        :param tag_type: The tag type, either "general", "travel", or "bus".
+        :param name: The name.
+        :param account: The associated account.
+        :param freq: The frequency of the tag name with the account.
+        :return: None.
+        """
+        self.__type_dict[tag_type].add_tag(name, account, freq)
+
+
+class SummaryHelper:
+    """The summary helper."""
+
+    def __init__(self):
+        """Constructs the summary helper."""
+        self.debit: SummaryEntryType = SummaryEntryType("debit")
+        """The debit tags."""
+        self.credit: SummaryEntryType = SummaryEntryType("credit")
+        """The credit tags."""
+        self.types: set[SummaryEntryType] = {self.debit, self.credit}
+        """The tags categorized by the entry types."""
+        entry_type: sa.Label = sa.case((JournalEntry.is_debit, "debit"),
+                                       else_="credit").label("entry_type")
+        tag_type: sa.Label = sa.case(
+            (JournalEntry.summary.like("_%—_%—_%→_%"), "bus"),
+            (sa.or_(JournalEntry.summary.like("_%—_%→_%"),
+                    JournalEntry.summary.like("_%—_%↔_%")), "travel"),
+            else_="general").label("tag_type")
+        tag: sa.Label = get_prefix(JournalEntry.summary, "—").label("tag")
+        select: sa.Select = sa.Select(entry_type, tag_type, tag,
+                                      JournalEntry.account_id,
+                                      sa.func.count().label("freq"))\
+            .filter(JournalEntry.summary.is_not(None),
+                    JournalEntry.summary.like("_%—_%"))\
+            .group_by(entry_type, tag_type, tag, JournalEntry.account_id)
+        result: list[sa.Row] = db.session.execute(select).all()
+        accounts: dict[int, Account] \
+            = {x.id: x for x in Account.query
+               .filter(Account.id.in_({x.account_id for x in result})).all()}
+        entry_type_dict: dict[t.Literal["debit", "credit"], SummaryEntryType] \
+            = {x.type: x for x in self.types}
+        for row in result:
+            entry_type_dict[row.entry_type].add_tag(
+                row.tag_type, row.tag, accounts[row.account_id], row.freq)
+
+
+def get_prefix(string: str | sa.Column, separator: str | sa.Column) \
+        -> sa.Function:
+    """Returns the SQL function to find the prefix of a string.
+
+    :param string: The string.
+    :param separator: The separator.
+    :return: The position of the substring, starting from 1.
+    """
+    return sa.func.substr(string, 0, get_position(string, separator))
+
+
+def get_position(string: str | sa.Column, substring: str | sa.Column) \
+        -> sa.Function:
+    """Returns the SQL function to find the position of a substring.
+
+    :param string: The string.
+    :param substring: The substring.
+    :return: The position of the substring, starting from 1.
+    """
+    if db.engine.name == "postgresql":
+        return sa.func.strpos(string, substring)
+    return sa.func.instr(string, substring)
diff --git a/tests/test_summary_helper.py b/tests/test_summary_helper.py
new file mode 100644
index 0000000..7a635ce
--- /dev/null
+++ b/tests/test_summary_helper.py
@@ -0,0 +1,327 @@
+# The Mia! Accounting Flask Project.
+# Author: imacat@mail.imacat.idv.tw (imacat), 2023/2/28
+
+#  Copyright (c) 2023 imacat.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+"""The test for the summary helper.
+
+"""
+import unittest
+from datetime import date
+
+from click.testing import Result
+from flask import Flask
+from flask.testing import FlaskCliRunner
+
+from test_site import create_app
+from testlib import get_client
+from testlib_txn import Accounts, NEXT_URI, add_txn
+
+
+class SummeryHelperTestCase(unittest.TestCase):
+    """The summary helper test case."""
+
+    def setUp(self) -> None:
+        """Sets up the test.
+        This is run once per test.
+
+        :return: None.
+        """
+        self.app: Flask = create_app(is_testing=True)
+
+        runner: FlaskCliRunner = self.app.test_cli_runner()
+        with self.app.app_context():
+            from accounting.models import BaseAccount, Transaction, \
+                JournalEntry
+            result: Result
+            result = runner.invoke(args="init-db")
+            self.assertEqual(result.exit_code, 0)
+            if BaseAccount.query.first() is None:
+                result = runner.invoke(args="accounting-init-base")
+                self.assertEqual(result.exit_code, 0)
+            result = runner.invoke(args=["accounting-init-currencies",
+                                         "-u", "editor"])
+            self.assertEqual(result.exit_code, 0)
+            result = runner.invoke(args=["accounting-init-accounts",
+                                         "-u", "editor"])
+            self.assertEqual(result.exit_code, 0)
+            Transaction.query.delete()
+            JournalEntry.query.delete()
+
+        self.client, self.csrf_token = get_client(self.app, "editor")
+
+    def test_summary_helper(self) -> None:
+        """Test the summary helper.
+
+        :return: None.
+        """
+        from accounting.transaction.summary_helper import SummaryHelper
+        for form in get_form_data(self.csrf_token):
+            add_txn(self.client, form)
+        with self.app.app_context():
+            helper: SummaryHelper = SummaryHelper()
+
+        # Debit-General
+        self.assertEqual(len(helper.debit.general.tags), 2)
+        self.assertEqual(helper.debit.general.tags[0].name, "Lunch")
+        self.assertEqual(len(helper.debit.general.tags[0].accounts), 2)
+        self.assertEqual(helper.debit.general.tags[0].accounts[0].code,
+                         Accounts.MEAL)
+        self.assertEqual(helper.debit.general.tags[0].accounts[1].code,
+                         Accounts.PAYABLE)
+        self.assertEqual(helper.debit.general.tags[1].name, "Dinner")
+        self.assertEqual(len(helper.debit.general.tags[1].accounts), 2)
+        self.assertEqual(helper.debit.general.tags[1].accounts[0].code,
+                         Accounts.MEAL)
+        self.assertEqual(helper.debit.general.tags[1].accounts[1].code,
+                         Accounts.PAYABLE)
+
+        # Debit-Travel
+        self.assertEqual(len(helper.debit.travel.tags), 3)
+        self.assertEqual(helper.debit.travel.tags[0].name, "Bike")
+        self.assertEqual(len(helper.debit.travel.tags[0].accounts), 1)
+        self.assertEqual(helper.debit.travel.tags[0].accounts[0].code,
+                         Accounts.TRAVEL)
+        self.assertEqual(helper.debit.travel.tags[1].name, "Taxi")
+        self.assertEqual(len(helper.debit.travel.tags[1].accounts), 1)
+        self.assertEqual(helper.debit.travel.tags[1].accounts[0].code,
+                         Accounts.TRAVEL)
+        self.assertEqual(helper.debit.travel.tags[2].name, "Airplane")
+        self.assertEqual(len(helper.debit.travel.tags[2].accounts), 1)
+        self.assertEqual(helper.debit.travel.tags[2].accounts[0].code,
+                         Accounts.TRAVEL)
+
+        # Debit-Bus
+        self.assertEqual(len(helper.debit.bus.tags), 2)
+        self.assertEqual(helper.debit.bus.tags[0].name, "Train")
+        self.assertEqual(len(helper.debit.bus.tags[0].accounts), 1)
+        self.assertEqual(helper.debit.bus.tags[0].accounts[0].code,
+                         Accounts.TRAVEL)
+        self.assertEqual(helper.debit.bus.tags[1].name, "Bus")
+        self.assertEqual(len(helper.debit.bus.tags[1].accounts), 1)
+        self.assertEqual(helper.debit.bus.tags[1].accounts[0].code,
+                         Accounts.TRAVEL)
+
+        # Credit-General
+        self.assertEqual(len(helper.credit.general.tags), 2)
+        self.assertEqual(helper.credit.general.tags[0].name, "Lunch")
+        self.assertEqual(len(helper.credit.general.tags[0].accounts), 3)
+        self.assertEqual(helper.credit.general.tags[0].accounts[0].code,
+                         Accounts.PAYABLE)
+        self.assertEqual(helper.credit.general.tags[0].accounts[1].code,
+                         Accounts.BANK)
+        self.assertEqual(helper.credit.general.tags[0].accounts[2].code,
+                         Accounts.CASH)
+        self.assertEqual(helper.credit.general.tags[1].name, "Dinner")
+        self.assertEqual(len(helper.credit.general.tags[1].accounts), 2)
+        self.assertEqual(helper.credit.general.tags[1].accounts[0].code,
+                         Accounts.BANK)
+        self.assertEqual(helper.credit.general.tags[1].accounts[1].code,
+                         Accounts.PAYABLE)
+
+        # Credit-Travel
+        self.assertEqual(len(helper.credit.travel.tags), 2)
+        self.assertEqual(helper.credit.travel.tags[0].name, "Bike")
+        self.assertEqual(len(helper.credit.travel.tags[0].accounts), 2)
+        self.assertEqual(helper.credit.travel.tags[0].accounts[0].code,
+                         Accounts.PAYABLE)
+        self.assertEqual(helper.credit.travel.tags[0].accounts[1].code,
+                         Accounts.PREPAID)
+        self.assertEqual(helper.credit.travel.tags[1].name, "Taxi")
+        self.assertEqual(len(helper.credit.travel.tags[1].accounts), 2)
+        self.assertEqual(helper.credit.travel.tags[1].accounts[0].code,
+                         Accounts.PAYABLE)
+        self.assertEqual(helper.credit.travel.tags[1].accounts[1].code,
+                         Accounts.CASH)
+
+        # Credit-Bus
+        self.assertEqual(len(helper.credit.bus.tags), 2)
+        self.assertEqual(helper.credit.bus.tags[0].name, "Train")
+        self.assertEqual(len(helper.credit.bus.tags[0].accounts), 2)
+        self.assertEqual(helper.credit.bus.tags[0].accounts[0].code,
+                         Accounts.PREPAID)
+        self.assertEqual(helper.credit.bus.tags[0].accounts[1].code,
+                         Accounts.PAYABLE)
+        self.assertEqual(helper.credit.bus.tags[1].name, "Bus")
+        self.assertEqual(len(helper.credit.bus.tags[1].accounts), 1)
+        self.assertEqual(helper.credit.bus.tags[1].accounts[0].code,
+                         Accounts.PREPAID)
+
+
+def get_form_data(csrf_token: str) -> list[dict[str, str]]:
+    """Returns the form data for multiple transaction forms.
+
+    :param csrf_token: The CSRF token.
+    :return: A list of the form data.
+    """
+    txn_date: str = date.today().isoformat()
+    return [{"csrf_token": csrf_token,
+             "next": NEXT_URI,
+             "date": txn_date,
+             "currency-0-code": "USD",
+             "currency-0-credit-0-account_code": Accounts.SERVICE,
+             "currency-0-credit-0-summary": " Salary ",
+             "currency-0-credit-0-amount": "2500"},
+            {"csrf_token": csrf_token,
+             "next": NEXT_URI,
+             "date": txn_date,
+             "currency-0-code": "USD",
+             "currency-0-debit-0-account_code": Accounts.MEAL,
+             "currency-0-debit-0-summary": " Lunch—Fish ",
+             "currency-0-debit-0-amount": "4.7",
+             "currency-0-credit-0-account_code": Accounts.BANK,
+             "currency-0-credit-0-summary": " Lunch—Fish ",
+             "currency-0-credit-0-amount": "4.7",
+             "currency-0-debit-1-account_code": Accounts.MEAL,
+             "currency-0-debit-1-summary": " Lunch—Fries ",
+             "currency-0-debit-1-amount": "2.15",
+             "currency-0-credit-1-account_code": Accounts.PAYABLE,
+             "currency-0-credit-1-summary": " Lunch—Fries ",
+             "currency-0-credit-1-amount": "2.15",
+             "currency-0-debit-2-account_code": Accounts.MEAL,
+             "currency-0-debit-2-summary": " Dinner—Hamburger ",
+             "currency-0-debit-2-amount": "4.25",
+             "currency-0-credit-2-account_code": Accounts.BANK,
+             "currency-0-credit-2-summary": " Dinner—Hamburger ",
+             "currency-0-credit-2-amount": "4.25"},
+            {"csrf_token": csrf_token,
+             "next": NEXT_URI,
+             "date": txn_date,
+             "currency-0-code": "USD",
+             "currency-0-debit-0-account_code": Accounts.MEAL,
+             "currency-0-debit-0-summary": " Lunch—Salad ",
+             "currency-0-debit-0-amount": "4.99",
+             "currency-0-credit-0-account_code": Accounts.CASH,
+             "currency-0-credit-0-summary": " Lunch—Salad ",
+             "currency-0-credit-0-amount": "4.99",
+             "currency-0-debit-1-account_code": Accounts.MEAL,
+             "currency-0-debit-1-summary": " Dinner—Steak ",
+             "currency-0-debit-1-amount": "8.28",
+             "currency-0-credit-1-account_code": Accounts.PAYABLE,
+             "currency-0-credit-1-summary": " Dinner—Steak ",
+             "currency-0-credit-1-amount": "8.28"},
+            {"csrf_token": csrf_token,
+             "next": NEXT_URI,
+             "date": txn_date,
+             "currency-0-code": "USD",
+             "currency-0-debit-0-account_code": Accounts.MEAL,
+             "currency-0-debit-0-summary": " Lunch—Pizza ",
+             "currency-0-debit-0-amount": "5.49",
+             "currency-0-credit-0-account_code": Accounts.PAYABLE,
+             "currency-0-credit-0-summary": " Lunch—Pizza ",
+             "currency-0-credit-0-amount": "5.49",
+             "currency-0-debit-1-account_code": Accounts.MEAL,
+             "currency-0-debit-1-summary": " Lunch—Noodles ",
+             "currency-0-debit-1-amount": "7.47",
+             "currency-0-credit-1-account_code": Accounts.PAYABLE,
+             "currency-0-credit-1-summary": " Lunch—Noodles ",
+             "currency-0-credit-1-amount": "7.47"},
+            {"csrf_token": csrf_token,
+             "next": NEXT_URI,
+             "date": txn_date,
+             "currency-0-code": "USD",
+             "currency-0-debit-0-account_code": Accounts.TRAVEL,
+             "currency-0-debit-0-summary": " Airplane—Lake City↔Hill Town ",
+             "currency-0-debit-0-amount": "800"},
+            {"csrf_token": csrf_token,
+             "next": NEXT_URI,
+             "date": txn_date,
+             "currency-0-code": "USD",
+             "currency-0-debit-0-account_code": Accounts.TRAVEL,
+             "currency-0-debit-0-summary": " Bus—323—Downtown→Museum ",
+             "currency-0-debit-0-amount": "2.5",
+             "currency-0-credit-0-account_code": Accounts.PREPAID,
+             "currency-0-credit-0-summary": " Bus—323—Downtown→Museum ",
+             "currency-0-credit-0-amount": "2.5",
+             "currency-0-debit-1-account_code": Accounts.TRAVEL,
+             "currency-0-debit-1-summary": " Train—Blue—Museum→Central ",
+             "currency-0-debit-1-amount": "3.2",
+             "currency-0-credit-1-account_code": Accounts.PREPAID,
+             "currency-0-credit-1-summary": " Train—Blue—Museum→Central ",
+             "currency-0-credit-1-amount": "3.2",
+             "currency-0-debit-2-account_code": Accounts.TRAVEL,
+             "currency-0-debit-2-summary": " Train—Green—Central→Mall ",
+             "currency-0-debit-2-amount": "3.2",
+             "currency-0-credit-2-account_code": Accounts.PREPAID,
+             "currency-0-credit-2-summary": " Train—Green—Central→Mall ",
+             "currency-0-credit-2-amount": "3.2",
+             "currency-0-debit-3-account_code": Accounts.TRAVEL,
+             "currency-0-debit-3-summary": " Train—Red—Mall→Museum ",
+             "currency-0-debit-3-amount": "4.4",
+             "currency-0-credit-3-account_code": Accounts.PAYABLE,
+             "currency-0-credit-3-summary": " Train—Red—Mall→Museum ",
+             "currency-0-credit-3-amount": "4.4"},
+            {"csrf_token": csrf_token,
+             "next": NEXT_URI,
+             "date": txn_date,
+             "currency-0-code": "USD",
+             "currency-0-debit-0-account_code": Accounts.TRAVEL,
+             "currency-0-debit-0-summary": " Taxi—Museum→Office ",
+             "currency-0-debit-0-amount": "15.5",
+             "currency-0-credit-0-account_code": Accounts.CASH,
+             "currency-0-credit-0-summary": " Taxi—Museum→Office ",
+             "currency-0-credit-0-amount": "15.5",
+             "currency-0-debit-1-account_code": Accounts.TRAVEL,
+             "currency-0-debit-1-summary": " Taxi—Office→Restaurant ",
+             "currency-0-debit-1-amount": "12",
+             "currency-0-credit-1-account_code": Accounts.PAYABLE,
+             "currency-0-credit-1-summary": " Taxi—Office→Restaurant ",
+             "currency-0-credit-1-amount": "12",
+             "currency-0-debit-2-account_code": Accounts.TRAVEL,
+             "currency-0-debit-2-summary": " Taxi—Restaurant→City Hall ",
+             "currency-0-debit-2-amount": "8",
+             "currency-0-credit-2-account_code": Accounts.PAYABLE,
+             "currency-0-credit-2-summary": " Taxi—Restaurant→City Hall ",
+             "currency-0-credit-2-amount": "8",
+             "currency-0-debit-3-account_code": Accounts.TRAVEL,
+             "currency-0-debit-3-summary": " Bike—City Hall→Office ",
+             "currency-0-debit-3-amount": "3.5",
+             "currency-0-credit-3-account_code": Accounts.PAYABLE,
+             "currency-0-credit-3-summary": " Bike—City Hall→Office ",
+             "currency-0-credit-3-amount": "3.5",
+             "currency-0-debit-4-account_code": Accounts.TRAVEL,
+             "currency-0-debit-4-summary": " Bike—Restaurant→Office ",
+             "currency-0-debit-4-amount": "4",
+             "currency-0-credit-4-account_code": Accounts.PAYABLE,
+             "currency-0-credit-4-summary": " Bike—Restaurant→Office ",
+             "currency-0-credit-4-amount": "4",
+             "currency-0-debit-5-account_code": Accounts.TRAVEL,
+             "currency-0-debit-5-summary": " Bike—Office→Theatre ",
+             "currency-0-debit-5-amount": "1.5",
+             "currency-0-credit-5-account_code": Accounts.PAYABLE,
+             "currency-0-credit-5-summary": " Bike—Office→Theatre ",
+             "currency-0-credit-5-amount": "1.5",
+             "currency-0-debit-6-account_code": Accounts.TRAVEL,
+             "currency-0-debit-6-summary": " Bike—Theatre→Home ",
+             "currency-0-debit-6-amount": "5.5",
+             "currency-0-credit-6-account_code": Accounts.PREPAID,
+             "currency-0-credit-6-summary": " Bike—Theatre→Home ",
+             "currency-0-credit-6-amount": "5.5"},
+            {"csrf_token": csrf_token,
+             "next": NEXT_URI,
+             "date": txn_date,
+             "currency-0-code": "USD",
+             "currency-0-debit-0-account_code": Accounts.PAYABLE,
+             "currency-0-debit-0-summary": " Dinner—Steak ",
+             "currency-0-debit-0-amount": "8.28",
+             "currency-0-credit-0-account_code": Accounts.BANK,
+             "currency-0-credit-0-summary": " Dinner—Steak ",
+             "currency-0-credit-0-amount": "8.28",
+             "currency-0-debit-1-account_code": Accounts.PAYABLE,
+             "currency-0-debit-1-summary": " Lunch—Pizza ",
+             "currency-0-debit-1-amount": "5.49",
+             "currency-0-credit-1-account_code": Accounts.BANK,
+             "currency-0-credit-1-summary": " Lunch—Pizza ",
+             "currency-0-credit-1-amount": "5.49"}]
+
diff --git a/tests/testlib_txn.py b/tests/testlib_txn.py
index 212ee11..1216fee 100644
--- a/tests/testlib_txn.py
+++ b/tests/testlib_txn.py
@@ -39,11 +39,14 @@ class Accounts:
     """The shortcuts to the common accounts."""
     CASH: str = "1111-001"
     BANK: str = "1113-001"
+    PREPAID: str = "1258-001"
+    PAYABLE: str = "2141-001"
     SALES: str = "4111-001"
     SERVICE: str = "4611-001"
     AGENCY: str = "4711-001"
     OFFICE: str = "6153-001"
     TRAVEL: str = "6154-001"
+    MEAL: str = "6172-001"
     INTEREST: str = "4111-001"
     DONATION: str = "7481-001"
     RENT: str = "7482-001"