diff --git a/datatypes/epc/domain/tests/test_from_site_notes.py b/datatypes/epc/domain/tests/test_from_site_notes.py
index be334e293..b5dd445b8 100644
--- a/datatypes/epc/domain/tests/test_from_site_notes.py
+++ b/datatypes/epc/domain/tests/test_from_site_notes.py
@@ -188,6 +188,39 @@ class TestGlazingTypeCoding:
             EpcPropertyDataMapper.from_site_notes(survey)
 
 
+class TestMainFuelCoding:
+    """`from_site_notes` must int-code the PAS Hub main-heating `fuel` label to the
+    SAP10 fuel code the calculator's cascade routes via, not copy the raw label. A
+    raw label reaches the calculator as `MissingMainFuelType`; an unmapped one
+    strict-raises `UnmappedPasHubLabel` at the boundary. `Bulk LPG` was the last
+    residual label parse-raising in the Guinness cohort (issue #1558); `Mains Gas`
+    is the capitalised variant the newer `Fuel:` site-note form lodges.
+    """
+
+    @pytest.mark.parametrize(
+        "label, expected_code",
+        [
+            ("Mains gas", 26),  # standard mains-gas fuel code (landed #1554)
+            ("Mains Gas", 26),  # `Fuel:` form capitalisation variant → same code
+            ("Bulk LPG", 27),  # bulk LPG (Table 32 code 2), matches Elmhurst map
+            ("Electricity", 30),  # standard-electricity fuel code
+        ],
+    )
+    def test_label_maps_to_sap_code(self, label: str, expected_code: int) -> None:
+        data = load("pashub_rdsap_site_notes_example1.json")
+        data["heating_and_hot_water"]["main_heating"]["fuel"] = label
+        survey = from_dict(PasHubRdSapSiteNotes, data)
+        result = EpcPropertyDataMapper.from_site_notes(survey)
+        assert result.sap_heating.main_heating_details[0].main_fuel_type == expected_code
+
+    def test_unknown_label_strict_raises(self) -> None:
+        data = load("pashub_rdsap_site_notes_example1.json")
+        data["heating_and_hot_water"]["main_heating"]["fuel"] = "Fusion reactor"
+        survey = from_dict(PasHubRdSapSiteNotes, data)
+        with pytest.raises(UnmappedPasHubLabel):
+            EpcPropertyDataMapper.from_site_notes(survey)
+
+
 class TestFromSiteNotesExample1:
     """
     Fixture: pashub_rdsap_site_notes_example1.json