implausible-lodged-score check fires for bad upstream EPC data (lodged < 13, gap >= 15) 🟩

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/audit/anomalies.py

@@ -191,7 +191,29 @@ def _effective_lodged_divergence(a: PropertyAudit) -> Optional[str]:
 
 @check("implausible-lodged-score", Severity.LOW)
 def _implausible_lodged_score(a: PropertyAudit) -> Optional[str]:
-    raise NotImplementedError
+    """Lodged SAP score is below 13 with a large effective-vs-lodged gap — the
+    lodged figure is implausible upstream EPC register data, not a modelling bug.
+
+    Floor of 13 is justified against the portfolio-796 distribution: every lodged
+    score below 13 either matches a known Class C exemplar (SAP 1: pids 727752,
+    727008, 731205) or shares the same bad-data fingerprint — implausibly low
+    lodged paired with a reasonable effective in band D/E (pids 710449 SAP 5,
+    722562 SAP 7, 725377 SAP 9, 727457 SAP 10, 723364 SAP 12). SAP 13 and above
+    are left in scope as ambiguous.
+
+    The gap guard (≥15) mirrors ``effective-lodged-divergence`` so the two checks
+    partition the same population without overlap."""
+    if a.lodged_sap is None or a.effective_sap is None:
+        return None
+    if a.lodged_sap >= 13:
+        return None
+    gap = a.effective_sap - a.lodged_sap
+    if abs(gap) < 15:
+        return None
+    return (
+        f"lodged SAP {a.lodged_sap:.0f} is implausible (< 13) — upstream EPC data,"
+        f" not a modelling bug (effective {a.effective_sap:.0f}, Δ{gap:+.0f})"
+    )
 
 
 @check("impossible-sap-over-100", Severity.HIGH)

tests/scripts/test_audit_anomalies.py

@@ -72,3 +72,23 @@ class TestImplausibleLodgedScore:
         # Assert
         assert result is not None
         assert "1" in result
+
+    def test_silent_when_gap_below_threshold(self) -> None:
+        # Arrange — lodged=9, effective=5 (gap -4, below ±15): both low, not a divergence anomaly
+        audit = _make_audit(lodged_sap=9.0, effective_sap=5.0)
+
+        # Act
+        result = _implausible_lodged_score(audit)
+
+        # Assert
+        assert result is None
+
+    def test_silent_when_lodged_sap_at_or_above_floor(self) -> None:
+        # Arrange — lodged=13 is on the floor boundary; effective=70 gives large gap
+        audit = _make_audit(lodged_sap=13.0, effective_sap=70.0)
+
+        # Act
+        result = _implausible_lodged_score(audit)
+
+        # Assert
+        assert result is None