diff --git a/homeassistant/components/anglian_water/sensor.py b/homeassistant/components/anglian_water/sensor.py
index c12dd45212e1..52cd629f8bbb 100644
--- a/homeassistant/components/anglian_water/sensor.py
+++ b/homeassistant/components/anglian_water/sensor.py
@@ -4,6 +4,7 @@ from __future__ import annotations
 
 from collections.abc import Callable
 from dataclasses import dataclass
+from datetime import datetime
 from enum import StrEnum
 
 from pyanglianwater.meter import SmartMeter
@@ -32,13 +33,14 @@ class AnglianWaterSensor(StrEnum):
     YESTERDAY_WATER_COST = "yesterday_water_cost"
     YESTERDAY_SEWERAGE_COST = "yesterday_sewerage_cost"
     LATEST_READING = "latest_reading"
+    LAST_UPDATED = "last_updated"
 
 
 @dataclass(frozen=True, kw_only=True)
 class AnglianWaterSensorEntityDescription(SensorEntityDescription):
     """Describes AnglianWater sensor entity."""
 
-    value_fn: Callable[[SmartMeter], float]
+    value_fn: Callable[[SmartMeter], float | datetime | None]
 
 
 ENTITY_DESCRIPTIONS: tuple[AnglianWaterSensorEntityDescription, ...] = (
@@ -76,6 +78,13 @@ ENTITY_DESCRIPTIONS: tuple[AnglianWaterSensorEntityDescription, ...] = (
         translation_key=AnglianWaterSensor.YESTERDAY_SEWERAGE_COST,
         entity_category=EntityCategory.DIAGNOSTIC,
     ),
+    AnglianWaterSensorEntityDescription(
+        key=AnglianWaterSensor.LAST_UPDATED,
+        device_class=SensorDeviceClass.TIMESTAMP,
+        value_fn=lambda entity: entity.last_updated,
+        translation_key=AnglianWaterSensor.LAST_UPDATED,
+        entity_category=EntityCategory.DIAGNOSTIC,
+    ),
 )
 
 
@@ -112,6 +121,6 @@ class AnglianWaterSensorEntity(AnglianWaterEntity, SensorEntity):
         self.entity_description = description
 
     @property
-    def native_value(self) -> float | None:
+    def native_value(self) -> float | datetime | None:
         """Return the state of the sensor."""
         return self.entity_description.value_fn(self.smart_meter)
diff --git a/homeassistant/components/anglian_water/strings.json b/homeassistant/components/anglian_water/strings.json
index 6db91b3b9b02..ae6895b98c88 100644
--- a/homeassistant/components/anglian_water/strings.json
+++ b/homeassistant/components/anglian_water/strings.json
@@ -34,6 +34,9 @@
   },
   "entity": {
     "sensor": {
+      "last_updated": {
+        "name": "Last meter reading processed"
+      },
       "latest_reading": {
         "name": "Latest reading"
       },
diff --git a/tests/components/anglian_water/conftest.py b/tests/components/anglian_water/conftest.py
index a5106f47791d..a482a7894555 100644
--- a/tests/components/anglian_water/conftest.py
+++ b/tests/components/anglian_water/conftest.py
@@ -3,6 +3,7 @@
 from collections.abc import AsyncGenerator, Generator
 from unittest.mock import AsyncMock, MagicMock, patch
 
+from freezegun.api import FrozenDateTimeFactory
 from pyanglianwater.api import API
 from pyanglianwater.meter import SmartMeter
 import pytest
@@ -32,20 +33,20 @@ def mock_config_entry() -> MockConfigEntry:
 
 
 @pytest.fixture
-def mock_smart_meter() -> SmartMeter:
-    """Return a mocked Smart Meter."""
-    mock = AsyncMock(spec=SmartMeter)
-    mock.serial_number = "TESTSN"
-    mock.get_yesterday_consumption = 50
-    mock.latest_read = 50
-    mock.yesterday_water_cost = 0.5
-    mock.yesterday_sewerage_cost = 0.5
-    mock.readings = [
+def mock_smart_meter(freezer: FrozenDateTimeFactory) -> SmartMeter:
+    """Return a Smart Meter for testing."""
+    # Freeze time to June 2, 2024 so "yesterday" is June 1, matching our test readings
+    freezer.move_to("2024-06-02T00:00:00Z")
+
+    meter = SmartMeter("TESTSN")
+    meter.readings = [
         {"read_at": "2024-06-01T12:00:00Z", "consumption": 10, "read": 10},
         {"read_at": "2024-06-01T13:00:00Z", "consumption": 15, "read": 25},
         {"read_at": "2024-06-01T14:00:00Z", "consumption": 25, "read": 50},
     ]
-    return mock
+    meter.yesterday_water_cost = 0.5
+    meter.yesterday_sewerage_cost = 0.5
+    return meter
 
 
 @pytest.fixture
diff --git a/tests/components/anglian_water/snapshots/test_sensor.ambr b/tests/components/anglian_water/snapshots/test_sensor.ambr
index 377509fb2e67..d75d7dd16785 100644
--- a/tests/components/anglian_water/snapshots/test_sensor.ambr
+++ b/tests/components/anglian_water/snapshots/test_sensor.ambr
@@ -1,4 +1,54 @@
 # serializer version: 1
+# name: test_sensor[sensor.testsn_last_meter_reading_processed-entry]
+  EntityRegistryEntrySnapshot({
+    'aliases': set({
+    }),
+    'area_id': None,
+    'capabilities': None,
+    'config_entry_id': <ANY>,
+    'config_subentry_id': <ANY>,
+    'device_class': None,
+    'device_id': <ANY>,
+    'disabled_by': None,
+    'domain': 'sensor',
+    'entity_category': <EntityCategory.DIAGNOSTIC: 'diagnostic'>,
+    'entity_id': 'sensor.testsn_last_meter_reading_processed',
+    'has_entity_name': True,
+    'hidden_by': None,
+    'icon': None,
+    'id': <ANY>,
+    'labels': set({
+    }),
+    'name': None,
+    'object_id_base': 'Last meter reading processed',
+    'options': dict({
+    }),
+    'original_device_class': <SensorDeviceClass.TIMESTAMP: 'timestamp'>,
+    'original_icon': None,
+    'original_name': 'Last meter reading processed',
+    'platform': 'anglian_water',
+    'previous_unique_id': None,
+    'suggested_object_id': None,
+    'supported_features': 0,
+    'translation_key': <AnglianWaterSensor.LAST_UPDATED: 'last_updated'>,
+    'unique_id': 'TESTSN_last_updated',
+    'unit_of_measurement': None,
+  })
+# ---
+# name: test_sensor[sensor.testsn_last_meter_reading_processed-state]
+  StateSnapshot({
+    'attributes': ReadOnlyDict({
+      'device_class': 'timestamp',
+      'friendly_name': 'TESTSN Last meter reading processed',
+    }),
+    'context': <ANY>,
+    'entity_id': 'sensor.testsn_last_meter_reading_processed',
+    'last_changed': <ANY>,
+    'last_reported': <ANY>,
+    'last_updated': <ANY>,
+    'state': '2024-06-01T14:00:00+00:00',
+  })
+# ---
 # name: test_sensor[sensor.testsn_latest_reading-entry]
   EntityRegistryEntrySnapshot({
     'aliases': set({
@@ -53,7 +103,7 @@
     'last_changed': <ANY>,
     'last_reported': <ANY>,
     'last_updated': <ANY>,
-    'state': '50',
+    'state': '50.0',
   })
 # ---
 # name: test_sensor[sensor.testsn_yesterday_s_sewerage_cost-entry]
@@ -161,7 +211,7 @@
     'last_changed': <ANY>,
     'last_reported': <ANY>,
     'last_updated': <ANY>,
-    'state': '50',
+    'state': '50.0',
   })
 # ---
 # name: test_sensor[sensor.testsn_yesterday_s_water_cost-entry]