From afe1801273dc5d382e50160e0de3460ccb05ed82 Mon Sep 17 00:00:00 2001
From: Daniel Roth <daniel_roth@hotmail.co.uk>
Date: Tue, 30 Jun 2026 15:27:19 +0000
Subject: [PATCH] =?UTF-8?q?implausible-lodged-score=20check=20fires=20for?=
 =?UTF-8?q?=20bad=20upstream=20EPC=20data=20(lodged=20<=2013,=20gap=20>=3D?=
 =?UTF-8?q?=2015)=20=F0=9F=9F=A9?=
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Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 scripts/audit/anomalies.py            | 24 +++++++++++++++++++++++-
 tests/scripts/test_audit_anomalies.py | 20 ++++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/scripts/audit/anomalies.py b/scripts/audit/anomalies.py
index 762fc30a5..b48b74015 100644
--- a/scripts/audit/anomalies.py
+++ b/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)
diff --git a/tests/scripts/test_audit_anomalies.py b/tests/scripts/test_audit_anomalies.py
index 69cd25080..280b7c3a9 100644
--- a/tests/scripts/test_audit_anomalies.py
+++ b/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