Name each benefit's LHA category and determination; drop dead UC LHA test inputs

changelog.d/lha-hb-category-followups.changed.md

@@ -0,0 +1 @@
+Document which Local Housing Allowance category and determination Housing Benefit and Universal Credit each read, and drop Universal Credit test inputs that the published rates no longer use.

docs/book/programs/gov/dwp/housing-benefit.ipynb

@@ -54,7 +54,7 @@
    "source": [
     "## Local Housing Allowance rates\n",
     "\n",
-    "A private renter's eligible rent is capped at the Local Housing Allowance (LHA) for their Broad Rental Market Area (BRMA) and LHA category: shared accommodation, or one to four bedrooms (`LHA_category`). Rent officers determine the rates each January for the year from April. In England this is the Valuation Office Agency, in Wales Rent Officers Wales, in Scotland Rent Service Scotland, and in Northern Ireland the Northern Ireland Housing Executive.\n",
+    "A private renter's eligible rent is capped at the Local Housing Allowance (LHA) for their Broad Rental Market Area (BRMA) and category of dwelling: shared accommodation, or one to four bedrooms. Housing Benefit has its own category (`housing_benefit_LHA_category`, [reg 13D](https://www.legislation.gov.uk/uksi/2006/213/regulation/13D) of the Housing Benefit Regulations 2006), and its rate is `housing_benefit_LHA_rate`; Universal Credit's category is `LHA_category`. Rent officers determine the rates each January for the year from April. In England this is the Valuation Office Agency, in Wales Rent Officers Wales, in Scotland Rent Service Scotland, and in Northern Ireland the Northern Ireland Housing Executive.\n",
     "\n",
     "PolicyEngine reads the published determinations from `parameters/gov/dwp/LHA/lha_published_rates.csv.gz`. `scripts/build_lha_published_rates.py` builds that table from the source files listed, with their hashes, in `lha_published_rates_sources.csv`. For each determination from April 2020, the rate is recomputed from the published 30th percentile rents, following [Schedule 3B](https://www.legislation.gov.uk/uksi/1997/1984/schedule/3B) to the Rent Officers (Housing Benefit Functions) Order 1997:\n",
     "\n",

policyengine_uk/tests/policy/baseline/finance/benefit/family/housing_benefit/housing_benefit_meals_deduction.yaml

@@ -171,13 +171,14 @@
       boarder_family:
         members: [boarder]
         meals_included_in_rent: AT_LEAST_THREE_A_DAY
-        uncapped_BRMA_LHA_rate: 9_000
     households:
       home:
         members: [householder, boarder]
         tenure_type: OWNED_OUTRIGHT
+        brma: MAIDSTONE
   output:
     # UC excludes food from service charges only in the social rented
     # sector and for owner-occupiers (UC Sch 1 para 8(1), (6)(c)); a private
-    # renter's whole payment is core rent: min(6,000, 9,000) = 6,000.
+    # renter's whole payment is core rent: min(6,000, Maidstone one-bedroom
+    # rate 750 a month = 9,000) = 6,000.
     uc_housing_costs_element: [0, 6_000]

policyengine_uk/tests/policy/baseline/finance/benefit/family/lha_published_rates.yaml

@@ -64,6 +64,18 @@
     BRMA_LHA_rate: 10_830.04
     uc_LHA_cap: 10_860
 
+- name: Maidstone one bedroom, April 2025, held at April 2024 (SI 2025/5)
+  period: 2025
+  absolute_error_margin: 0.01
+  input:
+    brma: MAIDSTONE
+    LHA_category: B
+    benunit_rent: 100_000
+  output:
+    # VOA: 172.60 a week x 52; DWP: 750.00 a month x 12.
+    BRMA_LHA_rate: 8_975.20
+    uc_LHA_cap: 9_000
+
 - name: Maidstone two bedrooms, April 2026, held at April 2024 (SI 2026/5)
   period: 2026
   absolute_error_margin: 0.01

policyengine_uk/tests/policy/baseline/finance/benefit/family/rent_of_sharers_boarders_and_lodgers.yaml

@@ -135,15 +135,16 @@
         members: [householder]
       lodger_family:
         members: [lodger]
-        uncapped_BRMA_LHA_rate: 6_000
     households:
       home:
         members: [householder, lodger]
         tenure_type: OWNED_OUTRIGHT
+        brma: MAIDSTONE
   output:
     benunit_rent: [0, 5_200]
     benunit_tenure_type: [OWNED_OUTRIGHT, RENT_PRIVATELY]
-    # UC: single, 40 >= 35, 1 bedroom: B. Cap = min(rent 5,200, rate 6,000).
+    # UC: single, 40 >= 35, 1 bedroom: B. Cap = min(rent 5,200, Maidstone
+    # one-bedroom rate 750 a month = 9,000).
     LHA_category: B
     uc_LHA_cap: [0, 5_200]
     uc_housing_costs_element: [0, 5_200]
@@ -164,17 +165,16 @@
     benunits:
       householder_family:
         members: [householder]
-        uncapped_BRMA_LHA_rate: 12_000
       daughter:
         members: [adult_daughter]
       lodger_family:
         members: [lodger]
-        uncapped_BRMA_LHA_rate: 6_000
     households:
       home:
         members: [householder, adult_daughter, lodger]
         rent: 10_000
         tenure_type: RENT_PRIVATELY
+        brma: MAIDSTONE
   output:
     # The daughter is the householder's non-dependant; the lodger is no one's
     # (UC Sch 4 para 9(2)(d)), and the householder's household is not the
@@ -183,8 +183,9 @@
     # One housing cost contribution, £93.02 a month for 2025-26 (Sch 4 para
     # 14): 93.02 x 12 = 1,116.24.
     uc_non_dep_deductions: [1_116.24, 0, 0]
-    # Householder: min(10,000, 12,000) - 1,116.24 = 8,883.76. The lodger's
-    # element is not reduced: min(5,200, 6,000) = 5,200.
+    # Householder (two bedrooms, C): min(10,000, Maidstone two-bedroom rate
+    # 905 a month = 10,860) - 1,116.24 = 8,883.76. The lodger's element is
+    # not reduced: min(5,200, one-bedroom rate 9,000) = 5,200.
     uc_housing_costs_element: [8_883.76, 0, 5_200]
     # UC bedrooms: householder 1 + daughter 1 = 2 (the lodger adds none).
     LHA_allowed_bedrooms: [2, 1, 1]
@@ -359,8 +360,8 @@
     # The pensioner head is not eligible for UC, so no other UC claim has
     # treated the non-dependant as one (UC Sch 4 para 9(2)(f)): they count
     # in the co-tenant's claim. Bedrooms 1 + 1 = 2: C. Core rent 18,000 / 2
-    # = 9,000, below the Maidstone two-bedroom rate (11,892.40); less one
-    # contribution of 93.02 x 12 = 1,116.24: 7,883.76.
+    # = 9,000, below the Maidstone two-bedroom rate (905 a month = 10,860);
+    # less one contribution of 93.02 x 12 = 1,116.24: 7,883.76.
     uc_non_dependants_counted: [false, true, false]
     LHA_allowed_bedrooms: [1, 2, 1]
     LHA_category: [B, C, A]

policyengine_uk/tests/test_mixed_age_couple_properties.py

@@ -53,6 +53,12 @@
 ]
 MIXED_AGE_COUPLE_SHAPES = {"mixed", "mixed_with_dependant"}
 TENURES = ["RENT_FROM_COUNCIL", "RENT_PRIVATELY", "OWNED_OUTRIGHT"]
+NORTH_WEST_BRMAS = [
+    "CENTRAL_GREATER_MANCHESTER",
+    "GREATER_LIVERPOOL",
+    "EAST_CHESHIRE",
+    "WEST_CUMBRIA",
+]
 
 
 # The three eligibility formulas as they were before the mixed-age couple
@@ -179,13 +185,14 @@ def cases(draw):
         "benunit": {
             "would_claim_uc": draw(st.booleans()),
             "would_claim_pc": draw(st.booleans()),
-            "BRMA_LHA_rate": draw(st.integers(4_000, 12_000)),
         },
         "household": {
             "tenure_type": tenure,
             "rent": 0 if tenure == "OWNED_OUTRIGHT" else draw(st.integers(0, 12_000)),
             "savings": draw(st.sampled_from([0, 5_000, 20_000])),
             "region": "NORTH_WEST",
+            # The LHA varies with the BRMA's published rates.
+            "brma": draw(st.sampled_from(NORTH_WEST_BRMAS)),
             "council_tax": 1_500,
         },
     }

policyengine_uk/utils/lha.py

@@ -420,10 +420,16 @@ def benunit_lha(
 ):
     """Look up an LHA measure for each benefit unit's BRMA and category.
 
-    ``category_variable`` names the category of accommodation: the Universal
-    Credit one by default, or ``housing_benefit_LHA_category``. Rent officers
-    determine one rate per BRMA and category, so the two benefits read the
-    same table; they differ only in which category applies to the renter.
+    ``universal_credit`` picks the determination: the weekly one under the
+    Rent Officers (Housing Benefit Functions) Order 1997, or the monthly one
+    under the Rent Officers (Universal Credit Functions) Order 2013.
+    ``category_variable`` names the category of accommodation to read it
+    for: the Universal Credit one by default, or
+    ``housing_benefit_LHA_category``. Each determination has one rate per
+    BRMA and category, so the benefits differ only in which determination
+    and which category they read: Housing Benefit the weekly table through
+    its own category (``housing_benefit_LHA_rate``), Universal Credit the
+    monthly table through ``LHA_category`` (``uc_LHA_cap``).
     """
     parameters = benunit.simulation.tax_benefit_system.parameters
     table = lha_rates(parameters, period.start.year, universal_credit)

policyengine_uk/variables/gov/dwp/BRMA_LHA_rate.py

@@ -5,10 +5,14 @@
 class BRMA_LHA_rate(Variable):
     value_type = float
     entity = BenUnit
-    label = "LHA rate"
+    label = "LHA rate (weekly determination, Universal Credit category)"
     documentation = (
-        "Weekly Housing Benefit Local Housing Allowance for the benefit unit's "
-        "Broad Rental Market Area and LHA category, annualised over 52 weeks"
+        "The weekly Local Housing Allowance determined for the benefit unit's "
+        "Broad Rental Market Area, read for its Universal Credit category "
+        "(LHA_category) and annualised over 52 weeks. Housing Benefit reads "
+        "the same weekly determination for its own category: see "
+        "housing_benefit_LHA_rate. Universal Credit uses the monthly "
+        "determination: see uc_LHA_cap."
     )
     definition_period = YEAR
     unit = GBP
@@ -18,7 +22,7 @@ class BRMA_LHA_rate(Variable):
     ]
 
     def formula(benunit, period, parameters):
-        """The determined Housing Benefit rate.
+        """The weekly determination, read for the Universal Credit category.
 
         The lower of the BRMA percentile rent and the weekly national maximum,
         raised to the rate of any smaller category and, from April 2024, to the

policyengine_uk/variables/gov/dwp/housing_benefit_LHA_rate.py

@@ -22,12 +22,12 @@ class housing_benefit_LHA_rate(Variable):
     def formula(benunit, period, parameters):
         """The determined Housing Benefit rate for the HB category.
 
-        The same determination as ``BRMA_LHA_rate`` (the lower of the BRMA
-        percentile rent and the weekly national maximum, the anomalous-rate
-        rule and, from April 2024, the 31 March 2020 minimum: Rent Officers
-        (Housing Benefit Functions) Order 1997, Schedule 3B paragraphs 2, 3
-        and 3A), read for the category in HB Regulations 2006 reg 13D rather
-        than the Universal Credit one.
+        The weekly determination that ``BRMA_LHA_rate`` reads (the lower of
+        the BRMA percentile rent and the weekly national maximum, the
+        anomalous-rate rule and, from April 2024, the 31 March 2020 minimum:
+        Rent Officers (Housing Benefit Functions) Order 1997, Schedule 3B
+        paragraphs 2, 3 and 3A), read for the category in HB Regulations 2006
+        reg 13D rather than the Universal Credit one.
         """
         return (
             benunit_lha(