MaxGhenis · Oct 22, 2026 · Oct 6, 2026 · Oct 9, 2026 · Oct 11, 2026 · Oct 11, 2026
diff --git a/changelog.d/corporate-sdlt-once.fixed.md b/changelog.d/corporate-sdlt-once.fixed.md
@@ -0,0 +1 @@
+- Count corporate SDLT once in `household_tax`, `gov_tax` and `pre_budget_change_household_tax`. `expected_sdlt` no longer adds `corporate_sdlt`, which those totals already list. `gov.hmrc.stamp_duty.abolish` now zeroes `corporate_sdlt` and the `stamp_duty_land_tax` liability (no household is `sdlt_liable` once the tax is abolished) as well as `expected_sdlt`, so abolishing SDLT removes all of it. `expected_sdlt` also no longer adds `property_sale_rate` (a 0.045 share) to every household as £0.045 of SDLT.
diff --git a/changelog.d/fiscal-partition.changed.md b/changelog.d/fiscal-partition.changed.md
@@ -0,0 +1 @@
+- Give corporate SDLT its own head in `policyengine_uk/data/fiscal_partition.yaml` now that the totals count it once, and empty `model_double_counts`. Each tax head now names its row of the OBR current receipts table (EFO November 2025, Table A.5) and, where the March 2026 EFO's Table 3.1 footnotes place it, that table's line. The file also lists the receipt rows the model does not cover, more exclusions (tax assessments, wage-change measures, income tax reductions) and more overlap guards. New tests check on simulated households that each tax total is the sum of its heads and counts each head once.
diff --git a/policyengine_uk/data/fiscal_partition.yaml b/policyengine_uk/data/fiscal_partition.yaml
diff --git a/policyengine_uk/tests/aggregate_impact/test_aggregate_impact_certified.py b/policyengine_uk/tests/aggregate_impact/test_aggregate_impact_certified.py
@@ -205,9 +205,9 @@ def numeric_lists(node):
 
 
 def test_geographic_guards_hold_once_declared_double_counts_are_netted(measured):
-    """Council tax and domestic rates never meet; nor do SDLT, LTT and LBTT
-    once corporate SDLT, which expected_sdlt carries while #2159 is open, is
-    netted out of it as a declared double count."""
+    """Council tax and domestic rates never meet; nor do SDLT, LTT and LBTT.
+    Since #2159 expected_sdlt carries no corporate SDLT, so nothing needs
+    netting here; a declared double count would be netted out of its head."""
     result, _, _, _ = measured
     status = {c["id"]: c["status"] for c in result["checks"]}
     assert status["overlap_guard:local_tax_geography"] == "pass"

diff --git a/policyengine_uk/tests/aggregate_impact/test_aggregate_impact_measure.py b/policyengine_uk/tests/aggregate_impact/test_aggregate_impact_measure.py
@@ -546,7 +546,7 @@ def calculate(self, variable, period, map_to=None, unweighted=True):
         return np.asarray(self.values.get(variable, np.zeros(self.n)), dtype=float)
 
 
-def _measured_year(values):
+def _measured_year(values, partition=None):
     from policyengine_uk.utils.aggregate_impact.measure import measure_year
     from policyengine_uk.utils.aggregate_impact.partition import (
         default_partition_path,
@@ -557,7 +557,7 @@ def _measured_year(values):
     rec.scope = "2026"
     measure_year(
         StubSim(values),
-        load_partition(default_partition_path()),
+        partition or load_partition(default_partition_path()),
         load_spec(),
         2026,
         rec,
@@ -566,6 +566,45 @@ def _measured_year(values):
     return rec, households
 
 
+def _corporate_sdlt_double_counted():
+    """The shipped partition in its shape before the #2159 fix: expected_sdlt
+    carries corporate SDLT, declared as a double count rather than a head.
+    The fix left the model with no double counts, so the tests of how a
+    declared one is measured use this."""
+    import yaml
+
+    from policyengine_uk.utils.aggregate_impact.partition import (
+        default_partition_path,
+        parse_partition,
+    )
+
+    with open(default_partition_path()) as f:
+        raw = yaml.safe_load(f)
+    totals = next(h for h in raw["tax_heads"] if h["id"] == "sdlt_corporate")["totals"]
+    raw["tax_heads"] = [h for h in raw["tax_heads"] if h["id"] != "sdlt_corporate"]
+
+    def repoint(ids):
+        return list(
+            dict.fromkeys("sdlt_household" if i == "sdlt_corporate" else i for i in ids)
+        )
+
+    for exclusion in raw["exclusions"]:
+        if exclusion.get("spans"):
+            exclusion["spans"] = repoint(exclusion["spans"])
+        if exclusion.get("head") == "sdlt_corporate":
+            exclusion["head"] = "sdlt_household"
+    for guard in raw["overlap_guards"]:
+        guard["heads"] = repoint(guard.get("heads") or [])
+    raw["model_double_counts"] = [
+        {
+            "variable": "corporate_sdlt",
+            "contained_in": "expected_sdlt",
+            "totals": totals,
+        }
+    ]
+    return parse_partition(raw)
+
+
 def _first(n, value):
     out = np.zeros(N)
     out[:n] = value
@@ -589,7 +628,8 @@ def test_a_double_count_from_few_records_is_suppressed_and_left_out():
             "household_tax": model_tax,
             "pre_budget_change_household_tax": model_tax,
             "gov_balance": model_tax,
-        }
+        },
+        _corporate_sdlt_double_counted(),
     )
     published = _published(rec)
     assert published["double_counts.corporate_sdlt"] is None

diff --git a/...ngine_uk/tests/policy/baseline/gov/hmrc/council_tax/high_value_council_tax_surcharge.yaml b/...ngine_uk/tests/policy/baseline/gov/hmrc/council_tax/high_value_council_tax_surcharge.yaml
@@ -7,7 +7,6 @@
     main_residential_property_purchased: 0
     council_tax: 0
     household_owns_tv: false
-    gov.hmrc.stamp_duty.property_sale_rate: 0
   output:
     high_value_council_tax_surcharge: 0
 - name: A 2028 value just above the first band on the annual 2026 HPI basis is charged
@@ -30,7 +29,6 @@
     main_residential_property_purchased: 0
     council_tax: 0
     household_owns_tv: false
-    gov.hmrc.stamp_duty.property_sale_rate: 0
   output:
     high_value_council_tax_surcharge: 2_500
     household_tax: 2_500
@@ -45,7 +43,6 @@
     main_residential_property_purchased: 0
     council_tax: 0
     household_owns_tv: false
-    gov.hmrc.stamp_duty.property_sale_rate: 0
   output:
     high_value_council_tax_surcharge: 2_550
     household_tax: 2_550
@@ -59,7 +56,6 @@
     main_residential_property_purchased: 0
     council_tax: 0
     household_owns_tv: false
-    gov.hmrc.stamp_duty.property_sale_rate: 0
   output:
     high_value_council_tax_surcharge: 0
     household_tax: 0
@@ -74,7 +70,6 @@
     main_residential_property_purchased: 0
     council_tax: 1_500
     household_owns_tv: false
-    gov.hmrc.stamp_duty.property_sale_rate: 0
   output:
     high_value_council_tax_surcharge: 2_500
     household_tax: 0

diff --git a/policyengine_uk/tests/policy/baseline/gov/hmrc/stamp_duty/corporate_sdlt.yaml b/policyengine_uk/tests/policy/baseline/gov/hmrc/stamp_duty/corporate_sdlt.yaml
@@ -0,0 +1,168 @@
+# Corporate SDLT is shareholding x (residential + non-residential corporate
+# SDLT revenue) = shareholding x (£705m + £2,425m) = shareholding x £3,130m
+# (gov.hmrc.stamp_duty.statistics, 2020 values held flat). A shareholding of
+# 1e-6 gives £3,130 and 3e-6 gives £9,390. business_rates is set to 0 so the
+# totals isolate SDLT. A £500,000 purchase that is not a first home pays
+# £15,000 of SDLT (see expected_sdlt.yaml).
+- name: Corporate SDLT enters household and government taxes once
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    region: LONDON
+    shareholding: 0.000001
+    business_rates: 0
+    council_tax: 0
+    household_owns_tv: false
+  output:
+    corporate_sdlt: 3_130
+    expected_sdlt: 0
+    corporate_tax_incidence: 3_130
+    household_tax: 3_130
+    gov_tax: 3_130
+    pre_budget_change_household_tax: 3_130
+- name: Household and corporate SDLT each enter the totals once
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    region: LONDON
+    main_residential_property_purchased: 500_000
+    main_residential_property_purchased_is_first_home: false
+    shareholding: 0.000001
+    business_rates: 0
+    council_tax: 0
+    household_owns_tv: false
+  output:
+    expected_sdlt: 15_000
+    corporate_sdlt: 3_130
+    household_tax: 18_130
+    gov_tax: 18_130
+    pre_budget_change_household_tax: 18_130
+- name: Abolishing SDLT removes household and corporate SDLT from the totals
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    gov.hmrc.stamp_duty.abolish: true
+    region: LONDON
+    main_residential_property_purchased: 500_000
+    main_residential_property_purchased_is_first_home: false
+    shareholding: 0.000001
+    business_rates: 0
+    council_tax: 0
+    household_owns_tv: false
+  output:
+    stamp_duty_land_tax: 0
+    expected_sdlt: 0
+    corporate_sdlt: 0
+    corporate_tax_incidence: 0
+    household_tax: 0
+    gov_tax: 0
+    pre_budget_change_household_tax: 0
+- name: Two households, baseline - each household's SDLT counted once
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      buyer:
+        age: 40
+      shareholder:
+        age: 60
+    benunits:
+      benunit_1:
+        members: [buyer]
+      benunit_2:
+        members: [shareholder]
+    households:
+      household_1:
+        members: [buyer]
+        region: LONDON
+        main_residential_property_purchased: 500_000
+        main_residential_property_purchased_is_first_home: false
+        shareholding: 0.000001
+        business_rates: 0
+        council_tax: 0
+        household_owns_tv: false
+      household_2:
+        members: [shareholder]
+        region: SCOTLAND
+        shareholding: 0.000003
+        business_rates: 0
+        council_tax: 0
+        household_owns_tv: false
+  output:
+    expected_sdlt: [15_000, 0]
+    corporate_sdlt: [3_130, 9_390]
+    household_tax: [18_130, 9_390]
+    gov_tax: [18_130, 9_390]
+- name: Two households, SDLT abolished - no SDLT left in either household's totals
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    gov.hmrc.stamp_duty.abolish: true
+    people:
+      buyer:
+        age: 40
+      shareholder:
+        age: 60
+    benunits:
+      benunit_1:
+        members: [buyer]
+      benunit_2:
+        members: [shareholder]
+    households:
+      household_1:
+        members: [buyer]
+        region: LONDON
+        main_residential_property_purchased: 500_000
+        main_residential_property_purchased_is_first_home: false
+        shareholding: 0.000001
+        business_rates: 0
+        council_tax: 0
+        household_owns_tv: false
+      household_2:
+        members: [shareholder]
+        region: SCOTLAND
+        shareholding: 0.000003
+        business_rates: 0
+        council_tax: 0
+        household_owns_tv: false
+  output:
+    expected_sdlt: [0, 0]
+    corporate_sdlt: [0, 0]
+    household_tax: [0, 0]
+    gov_tax: [0, 0]
+# Abolition removes SDLT and nothing else. Corporate SDLT reaches shareholders
+# wherever they live; business rates, the other corporate tax allocated by
+# shareholding, stays.
+- name: A Welsh shareholder bears corporate SDLT and business rates, each once
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    region: WALES
+    shareholding: 0.000001
+    business_rates: 500
+    council_tax: 0
+    household_owns_tv: false
+  output:
+    expected_sdlt: 0
+    corporate_sdlt: 3_130
+    corporate_tax_incidence: 3_630
+    household_tax: 3_630
+    gov_tax: 3_630
+    pre_budget_change_household_tax: 3_630
+- name: Abolishing SDLT removes the Welsh shareholder's corporate SDLT and keeps business rates
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    gov.hmrc.stamp_duty.abolish: true
+    region: WALES
+    shareholding: 0.000001
+    business_rates: 500
+    council_tax: 0
+    household_owns_tv: false
+  output:
+    expected_sdlt: 0
+    corporate_sdlt: 0
+    corporate_tax_incidence: 500
+    household_tax: 500
+    gov_tax: 500
+    pre_budget_change_household_tax: 500
diff --git a/policyengine_uk/tests/policy/baseline/gov/hmrc/stamp_duty/expected_sdlt.yaml b/policyengine_uk/tests/policy/baseline/gov/hmrc/stamp_duty/expected_sdlt.yaml
@@ -0,0 +1,82 @@
+# expected_sdlt is the household's own SDLT, with nothing added to it.
+# Residential rates from 1 April 2025 (gov.uk/stamp-duty-land-tax/residential-property-rates):
+# 0% to £125,000; 2% to £250,000; 5% to £925,000. A £500,000 purchase that is
+# not a first home pays 2% x £125,000 + 5% x £250,000 = £15,000.
+- name: No purchase and no corporate wealth means no SDLT in the tax totals (England)
+  period: 2026
+  absolute_error_margin: 0
+  input:
+    region: LONDON
+    council_tax: 0
+    household_owns_tv: false
+  output:
+    stamp_duty_land_tax: 0
+    expected_sdlt: 0
+    corporate_sdlt: 0
+    household_tax: 0
+    gov_tax: 0
+- name: No SDLT in the tax totals of a household outside England and Northern Ireland (Scotland)
+  period: 2026
+  absolute_error_margin: 0
+  input:
+    region: SCOTLAND
+    council_tax: 0
+    household_owns_tv: false
+  output:
+    expected_sdlt: 0
+    household_tax: 0
+    gov_tax: 0
+- name: No SDLT in the tax totals of a household outside England and Northern Ireland (Wales)
+  period: 2026
+  absolute_error_margin: 0
+  input:
+    region: WALES
+    council_tax: 0
+    household_owns_tv: false
+  output:
+    expected_sdlt: 0
+    household_tax: 0
+    gov_tax: 0
+- name: Expected SDLT on a purchase equals the SDLT liability
+  period: 2026
+  absolute_error_margin: 0
+  input:
+    region: LONDON
+    main_residential_property_purchased: 500_000
+    main_residential_property_purchased_is_first_home: false
+    council_tax: 0
+    household_owns_tv: false
+  output:
+    stamp_duty_land_tax: 15_000
+    expected_sdlt: 15_000
+    household_tax: 15_000
+    gov_tax: 15_000
+- name: Abolishing SDLT zeroes the liability and expected SDLT
+  period: 2026
+  absolute_error_margin: 0
+  input:
+    gov.hmrc.stamp_duty.abolish: true
+    region: LONDON
+    main_residential_property_purchased: 500_000
+    main_residential_property_purchased_is_first_home: false
+    council_tax: 0
+    household_owns_tv: false
+  output:
+    sdlt_liable: false
+    stamp_duty_land_tax: 0
+    expected_sdlt: 0
+    household_tax: 0
+    gov_tax: 0
+- name: Abolishing SDLT zeroes expected SDLT even when the liability is entered directly
+  period: 2026
+  absolute_error_margin: 0
+  input:
+    gov.hmrc.stamp_duty.abolish: true
+    region: LONDON
+    stamp_duty_land_tax: 15_000
+    council_tax: 0
+    household_owns_tv: false
+  output:
+    expected_sdlt: 0
+    household_tax: 0
+    gov_tax: 0
diff --git a/policyengine_uk/tests/policy/baseline/gov/hmrc/stamp_duty/sdlt_liable.yaml b/policyengine_uk/tests/policy/baseline/gov/hmrc/stamp_duty/sdlt_liable.yaml
@@ -4,3 +4,10 @@
     country: [ENGLAND, WALES, SCOTLAND, NORTHERN_IRELAND]
   output:
     sdlt_liable: [true, false, false, true]
+- name: No household is liable once Stamp Duty is abolished
+  period: 2026
+  input:
+    gov.hmrc.stamp_duty.abolish: true
+    country: [ENGLAND, WALES, SCOTLAND, NORTHERN_IRELAND]
+  output:
+    sdlt_liable: [false, false, false, false]
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		- Count corporate SDLT once in `household_tax`, `gov_tax` and `pre_budget_change_household_tax`. `expected_sdlt` no longer adds `corporate_sdlt`, which those totals already list. `gov.hmrc.stamp_duty.abolish` now zeroes `corporate_sdlt` and the `stamp_duty_land_tax` liability (no household is `sdlt_liable` once the tax is abolished) as well as `expected_sdlt`, so abolishing SDLT removes all of it. `expected_sdlt` also no longer adds `property_sale_rate` (a 0.045 share) to every household as £0.045 of SDLT.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		- Give corporate SDLT its own head in `policyengine_uk/data/fiscal_partition.yaml` now that the totals count it once, and empty `model_double_counts`. Each tax head now names its row of the OBR current receipts table (EFO November 2025, Table A.5) and, where the March 2026 EFO's Table 3.1 footnotes place it, that table's line. The file also lists the receipt rows the model does not cover, more exclusions (tax assessments, wage-change measures, income tax reductions) and more overlap guards. New tests check on simulated households that each tax total is the sum of its heads and counts each head once.