Fix pre-2027 property income tax main-rate reforms

changelog.d/2607.fixed.md

@@ -0,0 +1 @@
+- Made pre-2027 rUK property income follow reforms to the full main income-tax scale, while preserving separate property rates from 2027-28 and Scottish treatment.

policyengine_uk/tests/test_property_income_rate_reforms.py

@@ -0,0 +1,181 @@
+"""Property-rate routing before and from the model's annual 2027 period.
+
+Finance Act 2026 ss. 6(8) and 7 commence the separate property rates in
+2027-28. Earlier rUK property income follows the complete main-rate scale.
+The amounts below are independent marginal-band arithmetic, not snapshots.
+https://www.legislation.gov.uk/ukpga/2026/11/section/6/enacted
+https://www.legislation.gov.uk/ukpga/2026/11/section/7/enacted
+"""
+
+import pytest
+
+from policyengine_uk import Simulation
+
+pytestmark = pytest.mark.usefixtures("cloned_uk_tax_benefit_system")
+
+UK_RATE = "gov.hmrc.income_tax.rates.uk[{}].rate"
+PROPERTY_BASIC = "gov.hmrc.income_tax.rates.property.basic"
+RUK_COUNTRIES = ("ENGLAND", "WALES", "NORTHERN_IRELAND")
+
+
+def component_simulation(
+    year, earned, property_income, gift=0, country="ENGLAND", rates=None
+):
+    """Control taxable amounts after ordinary allowances to isolate the producer."""
+    return Simulation(
+        situation={
+            "people": {
+                "person": {
+                    "age": {year: 40},
+                    "non_savings_income_after_allowances": {
+                        year: earned + property_income
+                    },
+                    "taxable_property_income_after_allowances": {year: property_income},
+                    "gift_aid_grossed_up": {year: gift},
+                }
+            },
+            "benunits": {"benunit": {"members": ["person"]}},
+            "households": {
+                "household": {"members": ["person"], "country": {year: country}}
+            },
+        },
+        reform={path: {str(year): value} for path, value in (rates or {}).items()},
+    )
+
+
+@pytest.mark.parametrize("year", [2025, 2026])
+@pytest.mark.parametrize("country", RUK_COUNTRIES)
+@pytest.mark.parametrize(
+    "earned, bracket, rate, expected",
+    [(10_000, 0, 0.21, 1_050), (40_000, 1, 0.41, 2_050), (130_000, 2, 0.46, 2_300)],
+    ids=["basic", "higher", "additional"],
+)
+def test_pre_2027_property_income_uses_main_rate_reform(
+    year, country, earned, bracket, rate, expected
+):
+    sim = component_simulation(
+        year, earned, 5_000, country=country, rates={UK_RATE.format(bracket): rate}
+    )
+    assert sim.calculate("property_income_tax", year)[0] == pytest.approx(
+        expected, abs=0.01
+    )
+
+
+@pytest.mark.parametrize("year", [2025, 2026])
+@pytest.mark.parametrize(
+    "earned, gift, expected",
+    [(36_700, 0, 1_850), (36_700, 2_000, 1_450), (124_140, 2_000, 2_150)],
+    ids=["basic-higher", "gift-basic-higher", "gift-higher-additional"],
+)
+def test_main_rate_band_crossings_respect_gift_aid(year, earned, gift, expected):
+    rates = {UK_RATE.format(i): value for i, value in enumerate((0.21, 0.41, 0.46))}
+    sim = component_simulation(year, earned, 5_000, gift, rates=rates)
+    assert sim.calculate("property_income_tax", year)[0] == pytest.approx(
+        expected, abs=0.01
+    )
+
+
+@pytest.mark.parametrize("year", [2025, 2026])
+@pytest.mark.parametrize("gift", [0, 2_000])
+def test_pre_2027_property_income_uses_optional_fourth_main_bracket(year, gift):
+    sim = component_simulation(
+        year, 9_999_000, 5_000, gift, rates={UK_RATE.format(3): 0.60}
+    )
+    # Gift Aid extends statutory basic/higher limits, not this optional bracket.
+    assert sim.calculate("property_income_tax", year)[0] == pytest.approx(
+        1_000 * 0.45 + 4_000 * 0.60, abs=0.01
+    )
+
+
+@pytest.mark.parametrize("year", [2027, 2028])
+@pytest.mark.parametrize("country", RUK_COUNTRIES)
+def test_from_2027_main_rate_reform_leaves_separate_property_rate_unchanged(
+    year, country
+):
+    sim = component_simulation(
+        year, 10_000, 5_000, country=country, rates={UK_RATE.format(0): 0.21}
+    )
+    assert sim.calculate("property_income_tax", year)[0] == pytest.approx(
+        1_100, abs=0.01
+    )
+
+
+@pytest.mark.parametrize("year", [2027, 2028])
+def test_from_2027_separate_property_rate_reform_changes_property_tax(year):
+    sim = component_simulation(year, 10_000, 5_000, rates={PROPERTY_BASIC: 0.23})
+    assert sim.calculate("property_income_tax", year)[0] == pytest.approx(
+        1_150, abs=0.01
+    )
+
+
+@pytest.mark.parametrize("year", [2025, 2026])
+def test_pre_2027_separate_property_rate_reform_does_not_apply(year):
+    sim = component_simulation(year, 10_000, 5_000, rates={PROPERTY_BASIC: 0.99})
+    assert sim.calculate("property_income_tax", year)[0] == pytest.approx(
+        1_000, abs=0.01
+    )
+
+
+@pytest.mark.parametrize("year", [2025, 2026, 2027, 2028])
+def test_scottish_property_tax_keeps_scottish_rates_under_uk_reform(year):
+    rates = {UK_RATE.format(i): value for i, value in enumerate((0.21, 0.41, 0.46))}
+    sim = component_simulation(year, 40_000, 5_000, country="SCOTLAND", rates=rates)
+    assert sim.calculate("property_income_tax", year)[0] == pytest.approx(
+        5_000 * 0.42, abs=0.01
+    )
+
+
+@pytest.mark.parametrize("year", [2025, 2026])
+def test_scottish_gift_aid_band_crossing_is_unchanged(year):
+    sim = component_simulation(
+        year, 30_000, 5_000, 2_000, "SCOTLAND", {UK_RATE.format(1): 0.41}
+    )
+    assert sim.calculate("property_income_tax", year)[0] == pytest.approx(
+        3_092 * 0.21 + 1_908 * 0.42, abs=0.01
+    )
+
+
+@pytest.mark.parametrize("year", [2025, 2026, 2027, 2028])
+def test_zero_property_income_has_zero_property_tax_under_reform(year):
+    sim = component_simulation(year, 40_000, 0, rates={UK_RATE.format(1): 0.41})
+    assert sim.calculate("property_income_tax", year)[0] == 0
+
+
+@pytest.mark.parametrize(
+    "year, expected", [(2025, 1_000), (2026, 1_000), (2027, 1_100), (2028, 1_100)]
+)
+def test_baseline_property_rates_retain_annual_2027_boundary(year, expected):
+    sim = component_simulation(year, 10_000, 5_000)
+    assert sim.calculate("property_income_tax", year)[0] == pytest.approx(
+        expected, abs=0.01
+    )
+
+
+@pytest.mark.parametrize("country", RUK_COUNTRIES)
+def test_main_rate_reform_reaches_property_and_final_tax_from_natural_income(country):
+    year = 2026
+    sim = Simulation(
+        situation={
+            "people": {
+                "person": {
+                    "age": {year: 40},
+                    "employment_income": {year: 22_570},
+                    "property_income": {year: 5_000},
+                    "property_allowance_deduction": {year: 0},
+                }
+            },
+            "benunits": {"benunit": {"members": ["person"]}},
+            "households": {
+                "household": {"members": ["person"], "country": {year: country}}
+            },
+        },
+        reform={UK_RATE.format(0): {str(year): 0.21}},
+    )
+    assert sim.calculate("personal_allowance", year)[0] == 12_570
+    assert sim.calculate("non_savings_income_after_allowances", year)[0] == 15_000
+    assert sim.calculate("taxable_property_income_after_allowances", year)[0] == 5_000
+    assert sim.calculate("earned_income_tax", year)[0] == pytest.approx(2_100, abs=0.01)
+    assert sim.calculate("property_income_tax", year)[0] == pytest.approx(
+        1_050, abs=0.01
+    )
+    assert sim.calculate("income_tax", year)[0] == pytest.approx(3_150, abs=0.01)

policyengine_uk/variables/gov/hmrc/income_tax/liability/property_income_tax.py

@@ -6,6 +6,11 @@
 
 
 class property_income_tax(Variable):
+    """Tax on property income, following main UK rates before 2027-28 and
+    separate property rates thereafter for rUK taxpayers; Scottish
+    taxpayers retain the model's Scottish rate treatment.
+    """
+
     value_type = float
     entity = Person
     label = "Income tax on property income"
@@ -19,10 +24,51 @@ class property_income_tax(Variable):
             title="OBR Economic and Fiscal Outlook November 2025",
             href="https://obr.uk/efo/economic-and-fiscal-outlook-november-2025/",
         ),
+        dict(
+            title="Finance Act 2026, s. 6 (commencement in 2027-28)",
+            href="https://www.legislation.gov.uk/ukpga/2026/11/section/6/enacted",
+        ),
+        dict(
+            title="Finance Act 2026, s. 7 (property income rates)",
+            href="https://www.legislation.gov.uk/ukpga/2026/11/section/7/enacted",
+        ),
     ]
     unit = GBP
 
     def formula(person, period, parameters):
+        """Before 2027-28, property income uses the applicable main scale."""
+        rates = parameters(period).gov.hmrc.income_tax.rates
+        property_after_allowances = person(
+            "taxable_property_income_after_allowances", period
+        )
+        other_earned_taxable = max_(
+            0,
+            person("non_savings_income_after_allowances", period)
+            - property_after_allowances,
+        )
+        gross_gift = person("gift_aid_grossed_up", period)
+        ruk_tax = calc_income_tax_with_gift_aid(
+            rates.uk,
+            other_earned_taxable + property_after_allowances,
+            gross_gift,
+        ) - calc_income_tax_with_gift_aid(rates.uk, other_earned_taxable, gross_gift)
+        first_extended = first_extended_scottish_threshold(rates.scotland.rates)
+        scottish_tax = calc_income_tax_with_gift_aid(
+            rates.scotland.rates,
+            other_earned_taxable + property_after_allowances,
+            gross_gift,
+            first_extended,
+            len(rates.scotland.rates.thresholds),
+        ) - calc_income_tax_with_gift_aid(
+            rates.scotland.rates,
+            other_earned_taxable,
+            gross_gift,
+            first_extended,
+            len(rates.scotland.rates.thresholds),
+        )
+        return where(person("pays_scottish_income_tax", period), scottish_tax, ruk_tax)
+
+    def formula_2027(person, period, parameters):
         """
         Calculate income tax on property income.