diff --git a/corepos/db/office_op/model.py b/corepos/db/office_op/model.py
index f2a6884..c99f6a8 100644
--- a/corepos/db/office_op/model.py
+++ b/corepos/db/office_op/model.py
@@ -225,12 +225,18 @@ class Department(Base):
     Represents a department within the organization.
     """
     __tablename__ = 'departments'
+    __table_args__ = (
+        sa.ForeignKeyConstraint(['dept_tax'], ['taxrates.id']),
+    )
 
     number = sa.Column('dept_no', sa.SmallInteger(), primary_key=True, autoincrement=False, nullable=False)
 
     name = sa.Column('dept_name', sa.String(length=30), nullable=True)
 
-    tax = sa.Column('dept_tax', sa.Boolean(), nullable=True)
+    tax_rate_id = sa.Column('dept_tax', sa.SmallInteger(), nullable=True)
+    tax_rate = orm.relationship('TaxRate')
+    # TODO: deprecate / remove this
+    tax = orm.synonym('tax_rate_id')
 
     food_stampable = sa.Column('dept_fs', sa.Boolean(), nullable=True)