diff --git a/docs/api/wutta_corepos.db.model.rst b/docs/api/wutta_corepos.db.model.rst
new file mode 100644
index 0000000..9954c44
--- /dev/null
+++ b/docs/api/wutta_corepos.db.model.rst
@@ -0,0 +1,6 @@
+
+``wutta_corepos.db.model``
+==========================
+
+.. automodule:: wutta_corepos.db.model
+   :members:
diff --git a/docs/api/wutta_corepos.db.rst b/docs/api/wutta_corepos.db.rst
new file mode 100644
index 0000000..c04bb3e
--- /dev/null
+++ b/docs/api/wutta_corepos.db.rst
@@ -0,0 +1,6 @@
+
+``wutta_corepos.db``
+====================
+
+.. automodule:: wutta_corepos.db
+   :members:
diff --git a/docs/index.rst b/docs/index.rst
index 4f5d57b..a9beddd 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -5,8 +5,15 @@ Wutta-COREPOS
 This package adds basic integration with `CORE-POS`_, using
 `pyCOREPOS`_.
 
-Its main purpose is to setup DB connections for CORE Office, but it
-also contains basic readonly web views for some CORE tables.
+It provides the following:
+
+* standard configuration for CORE Office + Lane databases
+* special :term:`handler` for CORE integration
+  (:class:`~wutta_corepos.handler.CoreposHandler`)
+* readonly web views for primary CORE Office DB tables
+* :term:`data model` extension to map
+  :class:`~wuttjamaican:wuttjamaican.db.model.auth.User` to CORE
+  Employee
 
 .. _CORE-POS: https://www.core-pos.com/
 
@@ -26,6 +33,8 @@ also contains basic readonly web views for some CORE tables.
    api/wutta_corepos
    api/wutta_corepos.app
    api/wutta_corepos.conf
+   api/wutta_corepos.db
+   api/wutta_corepos.db.model
    api/wutta_corepos.handler
    api/wutta_corepos.web
    api/wutta_corepos.web.db
diff --git a/docs/narr/install.rst b/docs/narr/install.rst
index bceda1c..fdff505 100644
--- a/docs/narr/install.rst
+++ b/docs/narr/install.rst
@@ -39,3 +39,47 @@ related settings.
    02.url = mysql+mysqlconnector://lane02/translog
 
 And that's it, the CORE-POS integration is configured.
+
+
+Schema Extension
+----------------
+
+As of writing the only reason to add the schema extension is if you
+need to map Wutta Users to CORE Employees, for auth (login) purposes.
+So this section can be skipped if you do not need that.
+
+This will effectively add the
+:attr:`~wutta_corepos.db.model.CoreUser.corepos_employee_number`
+attribute on the
+:class:`~wuttjamaican:wuttjamaican.db.model.auth.User` model.
+
+First you must override the :term:`app model` with your own.  To do
+this, create your own module (e.g. ``poser.db.model``) to contain::
+
+   from wuttjamaican.db.model import *
+   from wutta_corepos.db.model import *
+
+Then configure your app model to override the default:
+
+.. code-block:: ini
+
+   [wutta]
+   model_spec = poser.db.model
+
+Then configure the Alembic section for schema migrations:
+
+.. code-block:: ini
+
+   [alembic]
+   script_location = wuttjamaican.db:alembic
+   version_locations = wutta_corepos.db:alembic/versions wuttjamaican.db:alembic/versions
+
+And finally run the Alembic command to migrate:
+
+.. code-block:: sh
+
+   cd /path/to/env
+   bin/alembic -c app/wutta.conf upgrade heads
+
+That should do it, from then on any changes will be migrated
+automatically during upgrade.
diff --git a/src/wutta_corepos/db/__init__.py b/src/wutta_corepos/db/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/wutta_corepos/db/alembic/versions/0f94089f1af1_initial_user_extension.py b/src/wutta_corepos/db/alembic/versions/0f94089f1af1_initial_user_extension.py
new file mode 100644
index 0000000..92ed240
--- /dev/null
+++ b/src/wutta_corepos/db/alembic/versions/0f94089f1af1_initial_user_extension.py
@@ -0,0 +1,37 @@
+"""initial user extension
+
+Revision ID: 0f94089f1af1
+Revises: 
+Create Date: 2025-01-24 21:13:14.359200
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+import wuttjamaican.db.util
+
+
+# revision identifiers, used by Alembic.
+revision: str = '0f94089f1af1'
+down_revision: Union[str, None] = None
+branch_labels: Union[str, Sequence[str], None] = ('wutta_corepos',)
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+
+    # corepos_user
+    op.create_table('corepos_user',
+                    sa.Column('uuid', wuttjamaican.db.util.UUID(), nullable=False),
+                    sa.Column('corepos_employee_number', sa.Integer(), nullable=False),
+                    sa.ForeignKeyConstraint(['uuid'], ['user.uuid'], name=op.f('fk_corepos_user_uuid_user')),
+                    sa.PrimaryKeyConstraint('uuid', name=op.f('pk_corepos_user')),
+                    sa.UniqueConstraint('corepos_employee_number', name=op.f('uq_corepos_user_corepos_employee_number'))
+                    )
+
+
+def downgrade() -> None:
+
+    # corepos_user
+    op.drop_table('corepos_user')
diff --git a/src/wutta_corepos/db/model.py b/src/wutta_corepos/db/model.py
new file mode 100644
index 0000000..89cf90d
--- /dev/null
+++ b/src/wutta_corepos/db/model.py
@@ -0,0 +1,67 @@
+# -*- coding: utf-8; -*-
+################################################################################
+#
+#  Wutta-COREPOS -- Wutta Framework integration for CORE-POS
+#  Copyright © 2025 Lance Edgar
+#
+#  This file is part of Wutta Framework.
+#
+#  Wutta Framework is free software: you can redistribute it and/or modify it
+#  under the terms of the GNU General Public License as published by the Free
+#  Software Foundation, either version 3 of the License, or (at your option) any
+#  later version.
+#
+#  Wutta Framework is distributed in the hope that it will be useful, but
+#  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+#  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+#  more details.
+#
+#  You should have received a copy of the GNU General Public License along with
+#  Wutta Framework.  If not, see <http://www.gnu.org/licenses/>.
+#
+################################################################################
+"""
+Data models for CORE-POS integration
+"""
+
+import sqlalchemy as sa
+from sqlalchemy import orm
+
+from wuttjamaican.db import model
+
+
+class CoreUser(model.Base):
+    """
+    CORE-POS extension for
+    :class:`~wuttjamaican:wuttjamaican.db.model.auth.User`.
+    """
+
+    __tablename__ = 'corepos_user'
+
+    uuid = model.uuid_column(sa.ForeignKey('user.uuid'), default=None)
+    user = orm.relationship(
+        model.User,
+        cascade_backrefs=False,
+        doc="""
+        Reference to the
+        :class:`~wuttjamaican:wuttjamaican.db.model.auth.User` which
+        this record extends.
+        """,
+        backref=orm.backref(
+            '_corepos',
+            uselist=False,
+            cascade='all, delete-orphan',
+            cascade_backrefs=False,
+            doc="""
+            Reference to the CORE-POS extension record for the user.
+            """)
+    )
+
+    corepos_employee_number = sa.Column(sa.Integer(), nullable=False, unique=True, doc="""
+    ``employees.emp_no`` value for the user within CORE-POS.
+    """)
+
+    def __str__(self):
+        return str(self.user)
+
+CoreUser.make_proxy(model.User, '_corepos', 'corepos_employee_number')
diff --git a/tests/db/test_model.py b/tests/db/test_model.py
new file mode 100644
index 0000000..19135d3
--- /dev/null
+++ b/tests/db/test_model.py
@@ -0,0 +1,16 @@
+# -*- coding: utf-8; -*-
+
+from wuttjamaican.testing import ConfigTestCase
+from wuttjamaican.db.model import User
+
+from wutta_corepos.db import model as mod
+
+
+class TestCoreUser(ConfigTestCase):
+
+    def test_str(self):
+        user = User(username='barney')
+        self.assertEqual(str(user), 'barney')
+
+        ext = mod.CoreUser(user=user, corepos_employee_number=42)
+        self.assertEqual(str(ext), 'barney')