diff --git a/alembic/versions/20260805_task_instance_period_label.py b/alembic/versions/20260805_task_instance_period_label.py
new file mode 100644
index 0000000..08c0fc5
--- /dev/null
+++ b/alembic/versions/20260805_task_instance_period_label.py
@@ -0,0 +1,56 @@
+"""add period label to client service task instances
+
+Revision ID: 20260805_task_instance_period_label
+Revises: 20260805_periodic_engagements
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy import inspect
+
+revision = "20260805_task_instance_period_label"
+down_revision = "20260805_periodic_engagements"
+branch_labels = None
+depends_on = None
+
+TABLE = "client_service_task_instances"
+INDEX = "ix_csti_period_label"
+
+
+def _inspector():
+    return inspect(op.get_bind())
+
+
+def _columns() -> set[str]:
+    return {row["name"] for row in _inspector().get_columns(TABLE)}
+
+
+def _indexes() -> set[str]:
+    return {row.get("name") for row in _inspector().get_indexes(TABLE) if row.get("name")}
+
+
+def upgrade():
+    if "period_label" not in _columns():
+        op.add_column(
+            TABLE,
+            sa.Column("period_label", sa.String(length=30), nullable=False, server_default=""),
+        )
+
+    op.execute(
+        """
+        UPDATE client_service_task_instances AS task
+        SET period_label = COALESCE(subscription.period_label, '')
+        FROM client_service_subscriptions AS subscription
+        WHERE task.subscription_id = subscription.id
+          AND COALESCE(task.period_label, '') = ''
+        """
+    )
+
+    if INDEX not in _indexes():
+        op.create_index(INDEX, TABLE, ["period_label"], unique=False)
+
+
+def downgrade():
+    if INDEX in _indexes():
+        op.drop_index(INDEX, table_name=TABLE)
+    if "period_label" in _columns():
+        op.drop_column(TABLE, "period_label")
diff --git a/app/modules/services/execution.py b/app/modules/services/execution.py
index 5172243..bc1d2f5 100644
--- a/app/modules/services/execution.py
+++ b/app/modules/services/execution.py
@@ -235,6 +235,7 @@ def generate_tasks_for_subscription(db: Session, *, subscription: ClientServiceS
                 service_catalogue_id=subscription.service_catalogue_id,
                 firm_task_template_id=template.id,
                 financial_year=subscription.financial_year,
+                period_label=getattr(subscription, "period_label", "") or "",
                 assessment_year=subscription.assessment_year,
                 task_name=template.task_name,
                 description=template.description,