diff --git a/changes.d/6362.fix.md b/changes.d/6362.fix.md
new file mode 100644
index 00000000000..d469ede6b95
--- /dev/null
+++ b/changes.d/6362.fix.md
@@ -0,0 +1 @@
+Fixed simulation mode bug where the task submit number would not increment
diff --git a/cylc/flow/workflow_db_mgr.py b/cylc/flow/workflow_db_mgr.py
index bb7a287e944..a541a238d7e 100644
--- a/cylc/flow/workflow_db_mgr.py
+++ b/cylc/flow/workflow_db_mgr.py
@@ -426,14 +426,15 @@ def put_update_task_state(self, itask):
             "status": itask.state.status,
             "flow_wait": itask.flow_wait,
             "is_manual_submit": itask.is_manual_submit,
+            "submit_num": itask.submit_num,
         }
+        # Note tasks_states table rows are for latest submit_num only
+        # (not one row per submit).
         where_args = {
             "cycle": str(itask.point),
             "name": itask.tdef.name,
             "flow_nums": serialise_set(itask.flow_nums),
         }
-        # Note tasks_states table rows are for latest submit_num only
-        # (not one row per submit).
         self.db_updates_map.setdefault(self.TABLE_TASK_STATES, [])
         self.db_updates_map[self.TABLE_TASK_STATES].append(
             (set_args, where_args))
diff --git a/tests/integration/test_simulation.py b/tests/integration/test_simulation.py
index c7e1b42fe27..49bc76ce5e2 100644
--- a/tests/integration/test_simulation.py
+++ b/tests/integration/test_simulation.py
@@ -15,11 +15,13 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from pathlib import Path
+
 import pytest
 from pytest import param
 
 from cylc.flow import commands
 from cylc.flow.cycling.iso8601 import ISO8601Point
+from cylc.flow.scheduler import Scheduler
 from cylc.flow.simulation import sim_time_check
 
 
@@ -443,3 +445,15 @@ async def test_settings_broadcast(
         assert itask.try_timers['execution-retry'].delays == [2.0, 2.0, 2.0]
         # n.b. rtconfig should remain unchanged, lest we cancel broadcasts:
         assert itask.tdef.rtconfig['execution retry delays'] == [5.0, 5.0]
+
+
+async def test_db_submit_num(
+    flow, one_conf, scheduler, run, complete, db_select
+):
+    """Test simulation mode correctly increments the submit_num in the DB."""
+    schd: Scheduler = scheduler(flow(one_conf), paused_start=False)
+    async with run(schd):
+        await complete(schd, '1/one')
+    assert db_select(schd, False, 'task_states', 'submit_num', 'status') == [
+        (1, 'succeeded'),
+    ]