Class 4 lower profits limit is £11,908 in 2023-24; NICA 2022 s.2 sets £12,570 from 6 April 2023 #1968

Problem

parameters/gov/hmrc/national_insurance/class_4/thresholds/lower_profits_limit.yaml dates the £12,570 lower profits limit (LPL) from 2024-01-01. Fiscal-year conversion samples each year at 30 April, so model year 2023 (2023-24) still uses the 2022-04-06 value of £11,908.

National Insurance Contributions (Increase of Thresholds) Act 2022 s.2 sets the dates:

• s.2(1)-(2) put £11,908 in SSCBA 1992 s.15(3)(a), treated as in force from 6 April 2022.
• s.2(3)-(4) substitute £12,570 from 6 April 2023.

So 2023-24 should use £12,570. In that year the primary threshold (52 × 241.73) and the personal allowance are already £12,570, so the LPL alone is out of line.

Existing tests pin the wrong 2023 value. tests/policy/baseline/gov/hmrc/national_insurance/class_4/ni_class_4.yaml expects 1,628 = 9% × (30,000 − 11,908) for 2023.

#1888 notes a related 2023 Class 4 problem: the model's 2023 additional rate is 3.5%, where s.15(3ZA) gives 2%. It leaves that for a separate fix. Worth checking both together, along with the main rate dates for 2022-23 and 2023-24.

Fix

• Date the £12,570 entry 2023-04-06.
• Check the Class 4 main and additional rate dates for 2022-23 and 2023-24 against s.15(3ZA) and the amending Acts.
• Update the 2023 tests and extend the LPL = PT × 52 = personal allowance alignment test in Hold NICs thresholds at 2026-27 levels through 2030-31 #1959 back to 2023.

Found while reviewing #1959, which does not change pre-2026 Class 4 values.