diff --git a/src/accounting/report/template_filters.py b/src/accounting/report/template_filters.py
new file mode 100644
index 0000000..53346ec
--- /dev/null
+++ b/src/accounting/report/template_filters.py
@@ -0,0 +1,37 @@
+# The Mia! Accounting Flask Project.
+# Author: imacat@mail.imacat.idv.tw (imacat), 2023/3/7
+
+#  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 template filters for the reports.
+
+"""
+from decimal import Decimal
+
+from accounting.template_filters import format_amount as core_format_amount
+
+
+def format_amount(value: Decimal | None) -> str | None:
+    """Formats an amount for the report.
+
+    :param value: The amount.
+    :return: The formatted amount text.
+    """
+    if value is None:
+        return ""
+    is_negative: bool = value < 0
+    formatted: str = core_format_amount(abs(value))
+    if is_negative:
+        formatted = f"({formatted})"
+    return formatted
diff --git a/src/accounting/report/views.py b/src/accounting/report/views.py
index 54e2709..395797c 100644
--- a/src/accounting/report/views.py
+++ b/src/accounting/report/views.py
@@ -24,9 +24,11 @@ from accounting.utils.permission import has_permission, can_view
 from .period import Period
 from .reports import Journal, Ledger, IncomeExpenses, TrialBalance, \
     IncomeStatement, BalanceSheet
+from .template_filters import format_amount
 
 bp: Blueprint = Blueprint("report", __name__)
 """The view blueprint for the reports."""
+bp.add_app_template_filter(format_amount, "accounting_report_format_amount")
 
 
 @bp.get("journal", endpoint="journal-default")
diff --git a/src/accounting/templates/accounting/report/balance-sheet.html b/src/accounting/templates/accounting/report/balance-sheet.html
index d1c9b26..d6373af 100644
--- a/src/accounting/templates/accounting/report/balance-sheet.html
+++ b/src/accounting/templates/accounting/report/balance-sheet.html
@@ -142,14 +142,14 @@ First written: 2023/3/7
                     <span class="d-none d-md-inline">{{ account.account.code }}</span>
                     {{ account.account.title|title }}
                   </div>
-                  <div class="accounting-amount">{{ account.amount|accounting_format_amount }}</div>
+                  <div class="accounting-amount {% if account.amount < 0 %} text-danger {% endif %}">{{ account.amount|accounting_report_format_amount }}</div>
                 </a>
               {% endfor %}
             {% endfor %}
           </div>
           <div class="d-md-none d-flex justify-content-between accounting-report-table-row accounting-balance-sheet-total">
             <div>{{ A_("Total") }}</div>
-            <div class="accounting-amount">{{ report.assets.total|accounting_format_amount }}</div>
+            <div class="accounting-amount {% if report.assets.total < 0 %} text-danger {% endif %}">{{ report.assets.total|accounting_report_format_amount }}</div>
           </div>
         {% endif %}
       </div>
@@ -173,14 +173,14 @@ First written: 2023/3/7
                     <span class="d-none d-md-inline">{{ account.account.code }}</span>
                     {{ account.account.title|title }}
                   </div>
-                  <div class="accounting-amount">{{ account.amount|accounting_format_amount }}</div>
+                  <div class="accounting-amount {% if account.amount < 0 %} text-danger {% endif %}">{{ account.amount|accounting_report_format_amount }}</div>
                 </a>
               {% endfor %}
             {% endfor %}
           </div>
           <div class="d-flex justify-content-between accounting-report-table-row accounting-balance-sheet-subtotal">
             <div>{{ A_("Total") }}</div>
-            <div class="accounting-amount">{{ report.liabilities.total|accounting_format_amount }}</div>
+            <div class="accounting-amount {% if report.liabilities.total < 0 %} text-danger {% endif %}">{{ report.liabilities.total|accounting_report_format_amount }}</div>
           </div>
         {% endif %}
 
@@ -202,20 +202,20 @@ First written: 2023/3/7
                     <span class="d-none d-md-inline">{{ account.account.code }}</span>
                     {{ account.account.title|title }}
                   </div>
-                  <div class="accounting-amount">{{ account.amount|accounting_format_amount }}</div>
+                  <div class="accounting-amount {% if account.amount < 0 %} text-danger {% endif %}">{{ account.amount|accounting_report_format_amount }}</div>
                 </a>
               {% endfor %}
             {% endfor %}
           </div>
           <div class="d-flex justify-content-between accounting-report-table-row accounting-balance-sheet-subtotal">
             <div>{{ A_("Total") }}</div>
-            <div class="accounting-amount">{{ report.owner_s_equity.total|accounting_format_amount }}</div>
+            <div class="accounting-amount {% if report.owner_s_equity.total < 0 %} text-danger {% endif %}">{{ report.owner_s_equity.total|accounting_report_format_amount }}</div>
           </div>
         {% endif %}
 
         <div class="d-md-none d-flex justify-content-between accounting-report-table-row accounting-balance-sheet-total">
           <div>{{ A_("Total") }}</div>
-          <div class="accounting-amount">{{ (report.liabilities.total + report.owner_s_equity.total)|accounting_format_amount }}</div>
+          <div class="accounting-amount {% if report.liabilities.total < 0 %} text-danger {% endif %}">{{ (report.liabilities.total + report.owner_s_equity.total)|accounting_report_format_amount }}</div>
         </div>
       </div>
     </div>
@@ -224,14 +224,14 @@ First written: 2023/3/7
       <div class="col-sm-6">
         <div class="d-flex justify-content-between accounting-balance-sheet-total">
           <div>{{ A_("Total") }}</div>
-          <div class="accounting-amount">{{ report.assets.total|accounting_format_amount }}</div>
+          <div class="accounting-amount {% if report.assets.total < 0 %} text-danger {% endif %}">{{ report.assets.total|accounting_report_format_amount }}</div>
         </div>
       </div>
 
       <div class="col-sm-6">
         <div class="d-flex justify-content-between accounting-balance-sheet-total">
           <div>{{ A_("Total") }}</div>
-          <div class="accounting-amount">{{ (report.liabilities.total + report.owner_s_equity.total)|accounting_format_amount }}</div>
+          <div class="accounting-amount {% if report.liabilities.total + report.owner_s_equity.total < 0 %} text-danger {% endif %}">{{ (report.liabilities.total + report.owner_s_equity.total)|accounting_report_format_amount }}</div>
         </div>
       </div>
     </div>
diff --git a/src/accounting/templates/accounting/report/income-expenses.html b/src/accounting/templates/accounting/report/income-expenses.html
index 12b3d8b..3bd4ec9 100644
--- a/src/accounting/templates/accounting/report/income-expenses.html
+++ b/src/accounting/templates/accounting/report/income-expenses.html
@@ -171,7 +171,7 @@ First written: 2023/3/5
             <div>{{ entry.summary|accounting_default }}</div>
             <div class="accounting-amount">{{ entry.income|accounting_format_amount|accounting_default }}</div>
             <div class="accounting-amount">{{ entry.expense|accounting_format_amount|accounting_default }}</div>
-            <div class="accounting-amount">{{ entry.balance|accounting_format_amount }}</div>
+            <div class="accounting-amount {% if entry.balance < 0 %} text-danger {% endif %}">{{ entry.balance|accounting_report_format_amount }}</div>
           </div>
         {% endwith %}
       {% endif %}
@@ -182,7 +182,7 @@ First written: 2023/3/5
           <div>{{ entry.summary|accounting_default }}</div>
           <div class="accounting-amount">{{ entry.income|accounting_format_amount|accounting_default }}</div>
           <div class="accounting-amount">{{ entry.expense|accounting_format_amount|accounting_default }}</div>
-          <div class="accounting-amount">{{ entry.balance|accounting_format_amount }}</div>
+          <div class="accounting-amount {% if entry.balance < 0 %} text-danger {% endif %}">{{ entry.balance|accounting_report_format_amount }}</div>
         </a>
       {% endfor %}
     </div>
@@ -193,7 +193,7 @@ First written: 2023/3/5
             <div>{{ A_("Total") }}</div>
             <div class="accounting-amount">{{ entry.income|accounting_format_amount }}</div>
             <div class="accounting-amount">{{ entry.expense|accounting_format_amount }}</div>
-            <div class="accounting-amount">{{ entry.balance|accounting_format_amount }}</div>
+            <div class="accounting-amount {% if entry.balance < 0 %} text-danger {% endif %}">{{ entry.balance|accounting_report_format_amount }}</div>
           </div>
         </div>
       {% endwith %}
diff --git a/src/accounting/templates/accounting/report/income-statement.html b/src/accounting/templates/accounting/report/income-statement.html
index 661f2e4..1d9c9ce 100644
--- a/src/accounting/templates/accounting/report/income-statement.html
+++ b/src/accounting/templates/accounting/report/income-statement.html
@@ -149,17 +149,17 @@ First written: 2023/3/7
                   <span class="d-none d-md-inline">{{ account.account.code }}</span>
                   {{ account.account.title|title }}
                 </div>
-                <div class="accounting-amount">{{ account.amount|accounting_format_amount }}</div>
+                <div class="accounting-amount {% if account.amount < 0 %} text-danger {% endif %}">{{ account.amount|accounting_report_format_amount }}</div>
               </a>
             {% endfor %}
             <div class="accounting-report-table-row accounting-income-statement-subtotal">
               <div>{{ A_("Total") }}</div>
-              <div class="accounting-amount">{{ subsection.total|accounting_format_amount }}</div>
+              <div class="accounting-amount {% if subsection.total < 0 %} text-danger {% endif %}">{{ subsection.total|accounting_report_format_amount }}</div>
             </div>
           {% endfor %}
           <div class="accounting-report-table-row accounting-income-statement-total">
             <div>{{ section.accumulated.title|title }}</div>
-            <div class="accounting-amount">{{ section.accumulated.amount|accounting_format_amount }}</div>
+            <div class="accounting-amount {% if section.accumulated.amount < 0 %} text-danger {% endif %}">{{ section.accumulated.amount|accounting_report_format_amount }}</div>
           </div>
         {% endfor %}
       </div>
diff --git a/src/accounting/templates/accounting/report/ledger.html b/src/accounting/templates/accounting/report/ledger.html
index 074b7ab..ed0bb27 100644
--- a/src/accounting/templates/accounting/report/ledger.html
+++ b/src/accounting/templates/accounting/report/ledger.html
@@ -169,7 +169,7 @@ First written: 2023/3/5
             <div>{{ entry.summary|accounting_default }}</div>
             <div class="accounting-amount">{{ entry.debit|accounting_format_amount|accounting_default }}</div>
             <div class="accounting-amount">{{ entry.credit|accounting_format_amount|accounting_default }}</div>
-            <div class="accounting-amount">{{ entry.balance|accounting_format_amount }}</div>
+            <div class="accounting-amount {% if entry.balance < 0 %} text-danger {% endif %}">{{ entry.balance|accounting_report_format_amount }}</div>
           </div>
         {% endwith %}
       {% endif %}
@@ -179,7 +179,7 @@ First written: 2023/3/5
           <div>{{ entry.summary|accounting_default }}</div>
           <div class="accounting-amount">{{ entry.debit|accounting_format_amount|accounting_default }}</div>
           <div class="accounting-amount">{{ entry.credit|accounting_format_amount|accounting_default }}</div>
-          <div class="accounting-amount">{{ entry.balance|accounting_format_amount }}</div>
+          <div class="accounting-amount {% if entry.balance < 0 %} text-danger {% endif %}">{{ entry.balance|accounting_report_format_amount }}</div>
         </a>
       {% endfor %}
     </div>
@@ -188,9 +188,9 @@ First written: 2023/3/5
         <div class="accounting-report-table-footer">
           <div class="accounting-report-table-row">
             <div>{{ A_("Total") }}</div>
-            <div class="accounting-amount">{{ entry.debit|accounting_format_amount }}</div>
-            <div class="accounting-amount">{{ entry.credit|accounting_format_amount }}</div>
-            <div class="accounting-amount">{{ entry.balance|accounting_format_amount }}</div>
+            <div class="accounting-amount">{{ entry.debit|accounting_default }}</div>
+            <div class="accounting-amount">{{ entry.credit|accounting_default }}</div>
+            <div class="accounting-amount {% if entry.balance < 0 %} text-danger {% endif %}">{{ entry.balance|accounting_report_format_amount }}</div>
           </div>
         </div>
       {% endwith %}