diff --git a/docs/source/examples.rst b/docs/source/examples.rst
index 552a9b0..fb1bc6b 100644
--- a/docs/source/examples.rst
+++ b/docs/source/examples.rst
@@ -13,7 +13,7 @@ The following is an example configuration for *Mia! Accounting*.
 
     from flask import Response, redirect
     from .auth import current_user()
-    from .modules import User
+    from .modules import Base, User
 
     def create_app(test_config=None) -> Flask:
         app: Flask = Flask(__name__)
@@ -36,6 +36,10 @@ The following is an example configuration for *Mia! Accounting*.
             def unauthorized(self) -> Response:
                 return redirect("/login")
 
+            @property
+            def base(self) -> type[DeclarativeBase]:
+                return Base
+
             @property
             def cls(self) -> type[User]:
                 return User
diff --git a/src/accounting/commands.py b/src/accounting/commands.py
index f342d8e..aa60a94 100644
--- a/src/accounting/commands.py
+++ b/src/accounting/commands.py
@@ -29,7 +29,7 @@ from .base_account import init_base_accounts_command
 from .currency import init_currencies_command
 from .models import BaseAccount, Account
 from .utils.title_case import title_case
-from .utils.user import has_user, get_user_pk
+from .utils.user import base_cls, has_user, get_user_pk
 
 
 def __validate_username(ctx: click.core.Context, param: click.core.Option,
@@ -62,7 +62,7 @@ def __validate_username(ctx: click.core.Context, param: click.core.Option,
 def init_db_command(username: str, skip_accounts: bool,
                     skip_currencies: bool) -> None:
     """Initializes the accounting database."""
-    db.create_all()
+    base_cls.metadata.create_all(db.engine)
     init_base_accounts_command()
     if not skip_accounts:
         init_accounts_command(username)
diff --git a/src/accounting/models.py b/src/accounting/models.py
index b8bb1ab..62dd295 100644
--- a/src/accounting/models.py
+++ b/src/accounting/models.py
@@ -31,10 +31,10 @@ from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from . import db
 from .locale import gettext
-from .utils.user import user_cls, user_pk_column
+from .utils.user import base_cls, user_cls, user_pk_column
 
 
-class BaseAccount(db.Model):
+class BaseAccount(base_cls):
     """A base account."""
     __tablename__ = "accounting_base_accounts"
     """The table name."""
@@ -78,7 +78,7 @@ class BaseAccount(db.Model):
         return [self.code, self.title_l10n] + [x.title for x in self.l10n]
 
 
-class BaseAccountL10n(db.Model):
+class BaseAccountL10n(base_cls):
     """A localized base account title."""
     __tablename__ = "accounting_base_accounts_l10n"
     """The table name."""
@@ -95,7 +95,7 @@ class BaseAccountL10n(db.Model):
     """The localized title."""
 
 
-class Account(db.Model):
+class Account(base_cls):
     """An account."""
     __tablename__ = "accounting_accounts"
     """The table name."""
@@ -354,7 +354,7 @@ class Account(db.Model):
         return account
 
 
-class AccountL10n(db.Model):
+class AccountL10n(base_cls):
     """A localized account title."""
     __tablename__ = "accounting_accounts_l10n"
     """The table name."""
@@ -371,7 +371,7 @@ class AccountL10n(db.Model):
     """The localized title."""
 
 
-class Currency(db.Model):
+class Currency(base_cls):
     """A currency."""
     __tablename__ = "accounting_currencies"
     """The table name."""
@@ -483,7 +483,7 @@ class Currency(db.Model):
         db.session.delete(self)
 
 
-class CurrencyL10n(db.Model):
+class CurrencyL10n(base_cls):
     """A localized currency name."""
     __tablename__ = "accounting_currencies_l10n"
     """The table name."""
@@ -543,7 +543,7 @@ class JournalEntryCurrency:
         return sum([x.amount for x in self.credit])
 
 
-class JournalEntry(db.Model):
+class JournalEntry(base_cls):
     """A journal entry."""
     __tablename__ = "accounting_journal_entries"
     """The table name."""
@@ -661,7 +661,7 @@ class JournalEntry(db.Model):
         db.session.delete(self)
 
 
-class JournalEntryLineItem(db.Model):
+class JournalEntryLineItem(base_cls):
     """A line item in the journal entry."""
     __tablename__ = "accounting_journal_entry_line_items"
     """The table name."""
@@ -888,7 +888,7 @@ class JournalEntryLineItem(db.Model):
                 format_amount(self.amount)]
 
 
-class Option(db.Model):
+class Option(base_cls):
     """An option."""
     __tablename__ = "accounting_options"
     """The table name."""
diff --git a/src/accounting/utils/random_id.py b/src/accounting/utils/random_id.py
index e37ba80..9f806f2 100644
--- a/src/accounting/utils/random_id.py
+++ b/src/accounting/utils/random_id.py
@@ -22,9 +22,10 @@ This module should not import any other module from the application.
 from secrets import randbelow
 
 from .. import db
+from ..utils.user import base_cls
 
 
-def new_id(cls: type[db.Model]):
+def new_id(cls: type[base_cls]):
     """Generates and returns a new, unused random ID for the data model.
 
     :param cls: The data model.
diff --git a/src/accounting/utils/user.py b/src/accounting/utils/user.py
index 8891d1b..3185c46 100644
--- a/src/accounting/utils/user.py
+++ b/src/accounting/utils/user.py
@@ -23,10 +23,10 @@ from abc import ABC, abstractmethod
 
 import sqlalchemy as sa
 from flask import g, Response
-from flask_sqlalchemy.model import Model
+from sqlalchemy.orm import DeclarativeBase
 
 
-class UserUtilityInterface[T: Model](ABC):
+class UserUtilityInterface[T: DeclarativeBase](ABC):
     """The interface for the user utilities."""
 
     @abstractmethod
@@ -67,6 +67,14 @@ class UserUtilityInterface[T: Model](ABC):
         :return: The response to require the user to log in.
         """
 
+    @property
+    @abstractmethod
+    def base(self) -> type[DeclarativeBase]:
+        """Returns the base data model.
+
+        :return: The base data model.
+        """
+
     @property
     @abstractmethod
     def cls(self) -> type[T]:
@@ -109,7 +117,9 @@ class UserUtilityInterface[T: Model](ABC):
 
 __user_utils: UserUtilityInterface
 """The user utilities."""
-type user_cls = Model
+base_cls = DeclarativeBase
+"""The base data model."""
+type user_cls = DeclarativeBase
 """The user class."""
 user_pk_column: sa.Column = sa.Column(sa.Integer)
 """The primary key column of the user class."""
@@ -121,8 +131,9 @@ def init_user_utils(utils: UserUtilityInterface) -> None:
     :param utils: The user utilities.
     :return: None.
     """
-    global __user_utils, user_cls, user_pk_column
+    global __user_utils, base_cls, user_cls, user_pk_column
     __user_utils = utils
+    base_cls = utils.base
     user_cls = utils.cls
     user_pk_column = utils.pk_column
 
diff --git a/tests/test_commands.py b/tests/test_commands.py
index 0f25b71..3cd2685 100644
--- a/tests/test_commands.py
+++ b/tests/test_commands.py
@@ -29,7 +29,7 @@ from flask import Flask
 from flask.testing import FlaskCliRunner
 from sqlalchemy.sql.ddl import DropTable
 
-from test_site import db
+from test_site import db, Base
 from testlib import create_test_app
 
 
@@ -63,7 +63,7 @@ class ConsoleCommandTestCase(unittest.TestCase):
             # Drop every accounting table, to see if accounting-init-db
             # recreates them correctly.
             tables: list[sa.Table] \
-                = [db.metadata.tables[x] for x in db.metadata.tables
+                = [Base.metadata.tables[x] for x in Base.metadata.tables
                    if x.startswith("accounting_")]
             for table in tables:
                 db.session.execute(DropTable(table))
@@ -207,7 +207,7 @@ class ConsoleCommandTestCase(unittest.TestCase):
         with self.__app.app_context():
             # Resets the accounts.
             tables: list[sa.Table] \
-                = [db.metadata.tables[x] for x in db.metadata.tables
+                = [Base.metadata.tables[x] for x in Base.metadata.tables
                    if x.startswith("accounting_")]
             for table in tables:
                 db.session.execute(DropTable(table))
diff --git a/tests/test_site/__init__.py b/tests/test_site/__init__.py
index 36cbf6b..6ee7598 100644
--- a/tests/test_site/__init__.py
+++ b/tests/test_site/__init__.py
@@ -28,6 +28,7 @@ from flask.testing import FlaskCliRunner
 from flask_babel_js import BabelJS
 from flask_sqlalchemy import SQLAlchemy
 from flask_wtf import CSRFProtect
+from sqlalchemy.orm import DeclarativeBase
 
 bp: Blueprint = Blueprint("home", __name__)
 """The global blueprint."""
@@ -39,6 +40,10 @@ db: SQLAlchemy = SQLAlchemy()
 """The database instance."""
 
 
+class Base(DeclarativeBase):
+    """The base class for all models."""
+
+
 def create_app(is_testing: bool = False, is_skip_accounts: bool = False,
                is_skip_currencies: bool = False) -> Flask:
     """Create and configure the application.
@@ -99,6 +104,10 @@ def create_app(is_testing: bool = False, is_skip_accounts: bool = False,
             from accounting.utils.next_uri import append_next
             return redirect(append_next(url_for("auth.login-form")))
 
+        @property
+        def base(self) -> type[DeclarativeBase]:
+            return Base
+
         @property
         def cls(self) -> type[auth.User]:
             return auth.User
@@ -137,7 +146,7 @@ def init_db(app: Flask, is_skip_accounts: bool,
         otherwise.
     :return: None.
     """
-    db.create_all()
+    Base.metadata.create_all(db.engine)
     from .auth import User
     for username in ["viewer", "editor", "admin", "nobody"]:
         user: User | None = db.session.scalar(
diff --git a/tests/test_site/auth.py b/tests/test_site/auth.py
index 1baaf4c..a408ea3 100644
--- a/tests/test_site/auth.py
+++ b/tests/test_site/auth.py
@@ -24,13 +24,13 @@ from flask import Blueprint, render_template, Flask, redirect, url_for, \
     session, request, g, Response, abort
 from sqlalchemy.orm import Mapped, mapped_column
 
-from . import db
+from . import db, Base
 
 bp: Blueprint = Blueprint("auth", __name__, url_prefix="/")
 """The authentication blueprint."""
 
 
-class User(db.Model):
+class User(Base):
     """A user."""
     __tablename__ = "users"
     """The table name."""