diff --git a/homeassistant/components/switch_as_x/entity.py b/homeassistant/components/switch_as_x/entity.py
index bc24460a105..ac56b4c6078 100644
--- a/homeassistant/components/switch_as_x/entity.py
+++ b/homeassistant/components/switch_as_x/entity.py
@@ -17,6 +17,8 @@ from homeassistant.helpers import entity_registry as er
 from homeassistant.helpers.entity import Entity, ToggleEntity
 from homeassistant.helpers.event import async_track_state_change_event
 
+from .const import DOMAIN as SWITCH_AS_X_DOMAIN
+
 
 class BaseEntity(Entity):
     """Represents a Switch as a X."""
@@ -28,8 +30,8 @@ class BaseEntity(Entity):
         name: str,
         switch_entity_id: str,
         unique_id: str | None,
-        device_id: str | None = None,
-        entity_category: EntityCategory | None = None,
+        device_id: str | None,
+        entity_category: EntityCategory | None,
     ) -> None:
         """Initialize Light Switch."""
         self._device_id = device_id
@@ -71,6 +73,11 @@ class BaseEntity(Entity):
         registry = er.async_get(self.hass)
         if registry.async_get(self.entity_id) is not None:
             registry.async_update_entity(self.entity_id, device_id=self._device_id)
+            registry.async_update_entity_options(
+                self.entity_id,
+                SWITCH_AS_X_DOMAIN,
+                {"entity_id": self._switch_entity_id},
+            )
 
 
 class BaseToggleEntity(BaseEntity, ToggleEntity):
diff --git a/tests/components/switch_as_x/test_init.py b/tests/components/switch_as_x/test_init.py
index 964e0a0d433..a95725999d9 100644
--- a/tests/components/switch_as_x/test_init.py
+++ b/tests/components/switch_as_x/test_init.py
@@ -438,3 +438,39 @@ async def test_entity_category_inheritance(
     assert entity_entry
     assert entity_entry.device_id == switch_entity_entry.device_id
     assert entity_entry.entity_category is EntityCategory.CONFIG
+
+
+@pytest.mark.parametrize("target_domain", PLATFORMS_TO_TEST)
+async def test_entity_options(
+    hass: HomeAssistant,
+    target_domain: Platform,
+) -> None:
+    """Test the source entity is stored as an entity option."""
+    registry = er.async_get(hass)
+
+    switch_entity_entry = registry.async_get_or_create("switch", "test", "unique")
+    registry.async_update_entity(
+        switch_entity_entry.entity_id, entity_category=EntityCategory.CONFIG
+    )
+
+    # Add the config entry
+    switch_as_x_config_entry = MockConfigEntry(
+        data={},
+        domain=DOMAIN,
+        options={
+            CONF_ENTITY_ID: switch_entity_entry.id,
+            CONF_TARGET_DOMAIN: target_domain,
+        },
+        title="ABC",
+    )
+    switch_as_x_config_entry.add_to_hass(hass)
+
+    assert await hass.config_entries.async_setup(switch_as_x_config_entry.entry_id)
+    await hass.async_block_till_done()
+
+    entity_entry = registry.async_get(f"{target_domain}.abc")
+    assert entity_entry
+    assert entity_entry.device_id == switch_entity_entry.device_id
+    assert entity_entry.options == {
+        DOMAIN: {"entity_id": switch_entity_entry.entity_id}
+    }