Count Carer's Allowance earnings-limit pence exactly

changelog.d/2541.fixed.md

@@ -0,0 +1 @@
+Fixed the Carer's Allowance earnings limit treating earnings a penny a week over the 2020-21 to 2024-25 limits (£128, £132, £139 and £151) as within them. Net earnings now apply the Computation of Earnings Regulations' rounding to each step: pay and profit are taken down to a whole penny and each calculated deduction (notional tax, Class 4 and half of pension contributions) up to one; the model's PAYE and Class 1, which in law are the amounts actually deducted, are rounded up too. Earnings are worked in double precision from the whole pence each amount was entered as, and a sum the model forms (pay, pension contributions, NI income) is the exact sum of its parts. Class 1 is worked out again from its formula where the model calculated it with that formula; entered as an input (for the year or month by month), or calculated under a reform, it is deducted as entered or calculated, its months summed exactly, so £1.20 entered is £1.20 deducted. The limit test reads the whole pence back exactly, so float32 rounding no longer decides it. Pension contributions entered as a total still reduce earnings. The Scottish Carer Support Payment, which reads the same earnings, is judged exactly at its limit too.

policyengine_uk/tests/policy/baseline/gov/dwp/carers_allowance_earnings_limit.yaml

@@ -5,7 +5,8 @@
 # are gross pay less income tax, primary Class 1 contributions and half of
 # pension contributions (Computation of Earnings Regulations 1996 reg.
 # 10(4)), and trading profit less a notional basic-rate tax and main-rate
-# Class 4 (regs. 13(4) and 14). A fraction of a penny is disregarded (reg. 5).
+# Class 4 (regs. 13(4) and 14). A fraction of a penny counts in the
+# claimant's favour (reg. 5): disregarded in earnings, a penny in a deduction.
 # 2026-27: personal allowance and NI primary threshold £12,570, employee
 # Class 1 main rate 8%, Class 4 lower profits limit £12,570 at 6%, basic rate
 # 20%. Carer's Allowance £86.45 a week.
@@ -321,3 +322,302 @@
     carers_allowance_earnings: 10_518.20
     is_gainfully_employed_for_carers_allowance: false
     carers_allowance_pre_overlap: 86.45 * 52
+
+- name: Case 21, in 2024-25 a penny a year short of £151.01 a week is within the limit.
+  period: 2024
+  absolute_error_margin: 0.01
+  input:
+    age: 45
+    employment_income: 7_852.51
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # 7,852.51 / 52 = £151.0098, which counts as £151.00 (reg. 5).
+    carers_allowance_earnings: 7_852.51
+    is_gainfully_employed_for_carers_allowance: false
+    carers_allowance: 81.90 * 52
+
+- name: Case 22, in 2024-25 a whole penny over £151 is over the limit.
+  period: 2024
+  absolute_error_margin: 0.01
+  input:
+    age: 45
+    employment_income: 7_852.52
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # 7,852.52 / 52 = £151.01. Float32 holds 7,852.52 as 7,852.52001953125;
+    # counting pence in float32 used to give £151.00 (#2541).
+    carers_allowance_earnings: 7_852.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0
+
+- name: Case 23, in 2024-25 the half penny of half an odd-pence pension contribution counts as a penny off earnings.
+  period: 2024
+  absolute_error_margin: 0.01
+  input:
+    age: 45
+    employment_income: 7_852.52
+    employee_pension_contributions: 0.01
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # Half of 0.01 is 0.005. Counting the half penny of the deduction as a
+    # penny favours the claimant (reg. 5), so earnings are 7,852.51, or
+    # £151.0098 a week, which counts as £151.00.
+    carers_allowance_earnings: 7_852.51
+    is_gainfully_employed_for_carers_allowance: false
+    carers_allowance: 81.90 * 52
+
+- name: Case 24, in 2024-25 a penny more pay with the same contribution is over the limit.
+  period: 2024
+  absolute_error_margin: 0.01
+  input:
+    age: 45
+    employment_income: 7_852.53
+    employee_pension_contributions: 0.01
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # 7,852.53 less 0.01 (the half penny counted as a penny) is 7,852.52, or
+    # £151.01 a week.
+    carers_allowance_earnings: 7_852.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0
+
+- name: Case 25, a fraction of a penny in each self-employed deduction counts as a penny.
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    self_employment_income: 14_000.01
+    personal_pension_contributions: 6_039.38
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # Notional tax 20% x 1,430.01 = 286.002 and Class 4 6% x 1,430.01 =
+    # 85.8006 count as 286.01 and 85.81 (reg. 5), and half the premium is
+    # 3,019.69: 14,000.01 - 286.01 - 85.81 - 3,019.69 = 10,608.50, or £204.00
+    # a week, within the limit. Unrounded, earnings are 10,608.5174; the
+    # nearest half penny of that is 10,608.52, £204.01 a week, which would
+    # have ended entitlement (juaristi22's review of #2543).
+    carers_allowance_earnings: 10_608.50
+    is_gainfully_employed_for_carers_allowance: false
+    carers_allowance: 86.45 * 52
+
+- name: Case 26, in 2026-27 a whole penny of Class 1 counts as that penny, not two.
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    employment_income: 14_764.46
+    employee_pension_contributions: 7_960.76
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # Class 1 is 8% x (14,764.46 - 52 x 241.73) = 175.56 exactly; the model's
+    # float32 sum of twelve months holds it as 175.5600128, which rounded up
+    # would be 175.57. Pay less the contribution is 6,803.70, under the
+    # personal allowance, so no PAYE, and half the contribution is 3,980.38:
+    # 14,764.46 - 175.56 - 3,980.38 = 10,608.52, or £204.01 a week, over the
+    # limit.
+    carers_allowance_earnings: 10_608.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0
+
+- name: Case 27, in 2025-26 the same Class 1 of £175.56 leaves a penny a week over £196.
+  period: 2025
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    employment_income: 14_764.46
+    employee_pension_contributions: 8_792.76
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # 14,764.46 - 175.56 - 4,396.38 = 10,192.52, or £196.01 a week.
+    carers_allowance_earnings: 10_192.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0
+
+- name: Case 28, in 2024-25 Class 1 of £43.80 leaves a penny a week over £151.
+  period: 2024
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    employment_income: 13_117.46
+    employee_pension_contributions: 10_442.27
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # Class 1 is 8% x (13,117.46 - 12,569.96) = 43.80, stored as 43.800003.
+    # Half the contribution is 5,221.135, which counts as 5,221.14 (reg. 5):
+    # 13,117.46 - 43.80 - 5,221.14 = 7,852.52, or £151.01 a week.
+    carers_allowance_earnings: 7_852.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0
+
+- name: Case 29, pension contributions entered as a total still come off earnings.
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    employment_income: 11_000
+    pension_contributions: 1_000
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # 11,000 - 1,000 / 2 = 10,500, or £201.92 a week, within the limit.
+    carers_allowance_earnings: 10_500
+    is_gainfully_employed_for_carers_allowance: false
+    carers_allowance: 86.45 * 52
+
+- name: Case 30, in 2026-27 £12,570.50 of profit with a £3,923.70 premium is a penny a week over the limit.
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    self_employment_income: 12_570.50
+    personal_pension_contributions: 3_923.70
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # Notional tax 20% x 0.50 = 0.10 and Class 4 6% x 0.50 = 0.03:
+    # 12,570.50 - 0.10 - 0.03 - 1,961.85 = 10,608.52, £204.01 a week.
+    carers_allowance_earnings: 10_608.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0
+
+- name: Case 31, a penny more profit can leave a penny less in earnings, as reg. 5 intends.
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    self_employment_income: 12_570.51
+    personal_pension_contributions: 3_923.70
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # Notional tax 0.102 and Class 4 0.0306 each count as a penny more (0.11
+    # and 0.04), so the extra penny of profit adds two pennies of deductions:
+    # 12,570.51 - 0.11 - 0.04 - 1,961.85 = 10,608.51, £204.00 a week, within.
+    carers_allowance_earnings: 10_608.51
+    is_gainfully_employed_for_carers_allowance: false
+    carers_allowance: 86.45 * 52
+
+- name: Case 32, two pension programmes are summed in whole pence, not as float32 adds them.
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    employment_income: 12_229.84
+    employee_pension_contributions: 1_807.49
+    personal_pension_contributions: 1_435.15
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # The contributions total 3,242.64, which pension_contributions holds as
+    # 3,242.64013671875: more than half a float32 step out, so read alone it
+    # would be 3,242.6401367 and half of it would count as 1,621.33. Summed
+    # in whole pence, half is 1,621.32. Pay is under the primary threshold,
+    # and pay less the employee contribution under the personal allowance:
+    # 12,229.84 - 1,621.32 = 10,608.52, or £204.01 a week, over the limit.
+    carers_allowance_earnings: 10_608.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0
+
+- name: Case 33, Class 1 entered as nil is deducted as nil, not as the formula would work it.
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    employment_income: 12_569.97
+    employee_pension_contributions: 3_922.90
+    ni_class_1_employee: 0
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # The model's formula would charge 8% of the penny over its £12,569.96
+    # primary threshold, 0.0008, counted as a penny. Entered as nil, nil is
+    # what was deducted (reg. 10(4)(a)): 12,569.97 - 3,922.90 / 2 = 10,608.52,
+    # or £204.01 a week, over the limit.
+    carers_allowance_earnings: 10_608.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0
+
+- name: Case 34, a pension total the model sums from two inputs is read in whole pence.
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    employment_income_before_lsr: 10_608.96
+    salary_sacrifice_returned_to_income: 0.20
+    employee_pension_contributions_reported: 1.08
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # Pay is 10,608.96 + 0.20 = 10,609.16; employee contributions are
+    # 1.08 + 0.20 = 1.28, which float32 adds to 1.28000009, so that half of
+    # it read alone would count as 0.65. Summed in whole pence, half is 0.64:
+    # 10,609.16 - 0.64 = 10,608.52, or £204.01 a week, over the limit.
+    carers_allowance_earnings: 10_608.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0
+
+- name: Case 35, pay the model sums from two inputs is read in whole pence.
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    employment_income_before_lsr: 10_276.42
+    salary_sacrifice_returned_to_income: 1_415.69
+    employee_pension_contributions_reported: 751.49
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # Pay is 10,276.42 + 1,415.69 = 11,692.11, which float32 adds to
+    # 11,692.109375: more than half a float32 step out, so read alone it would
+    # count as 11,692.10. Contributions are 751.49 + 1,415.69 = 2,167.18, half
+    # 1,083.59. Pay is under the primary threshold and pay less contributions
+    # under the personal allowance: 11,692.11 - 1,083.59 = 10,608.52, or
+    # £204.01 a week, over the limit.
+    carers_allowance_earnings: 10_608.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0
+
+- name: Case 36, pay and pension both summed by the model are read in whole pence.
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    employment_income_before_lsr: 10_794.69
+    salary_sacrifice_returned_to_income: 1_435.15
+    employee_pension_contributions_reported: 1_807.49
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # Pay is 10,794.69 + 1,435.15 = 12,229.84 (float32: 12,229.8408203125)
+    # and contributions 1,807.49 + 1,435.15 = 3,242.64 (3,242.64013671875),
+    # each more than half a float32 step out of its pence. Summed in whole
+    # pence: 12,229.84 - 3,242.64 / 2 = 10,608.52, or £204.01 a week, over.
+    carers_allowance_earnings: 10_608.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0
+
+- name: Case 37, Class 1 entered for the year in whole pence is deducted in whole pence.
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    employment_income: 10_609.72
+    ni_class_1_employee: 1.20
+    care_hours: 40
+    country: ENGLAND
+  output:
+    # The model divides the year's 1.20 among the months in float32 and
+    # sums them to 1.2000002, which rounded up would deduct 1.21. The Class
+    # 1 deducted is the 1.20 entered (reg. 10(4)(a)): 10,609.72 - 1.20 =
+    # 10,608.52, or £204.01 a week, over the limit.
+    carers_allowance_earnings: 10_608.52
+    is_gainfully_employed_for_carers_allowance: true
+    carers_allowance: 0

policyengine_uk/tests/policy/baseline/gov/social_security_scotland/carer_support_payment_earnings_limit.yaml

@@ -441,3 +441,33 @@
   output:
     carers_allowance_earnings: 6146.6
     carer_support_payment_pre_overlap: 0
+
+- name: Each self-employed deduction rounded up a penny leaves earnings within the limit
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    self_employment_income: 12576.76
+    personal_pension_contributions: 3932.96
+    care_hours: 40
+    country: SCOTLAND
+  output:
+    # Sch2para4: notional tax 20% x 6.76 = 1.352 and Class 4 6% x 6.76 =
+    # 0.4056 count as 1.36 and 0.41; half the premium is 1,966.48:
+    # 12,576.76 - 1.36 - 0.41 - 1,966.48 = 10,608.51, or 204.00 a week.
+    carers_allowance_earnings: 10608.51
+    carer_support_payment_pre_overlap: 4495.4
+
+- name: A penny more profit leaves earnings a penny a week over the limit
+  period: 2026
+  absolute_error_margin: 0.001
+  input:
+    age: 45
+    self_employment_income: 12576.77
+    personal_pension_contributions: 3932.96
+    care_hours: 40
+    country: SCOTLAND
+  output:
+    # 12,576.77 - 1.36 - 0.41 - 1,966.48 = 10,608.52, or 204.01 a week.
+    carers_allowance_earnings: 10608.52
+    carer_support_payment_pre_overlap: 0