# payroll.statutory-maternity-pay

Statutory Maternity Pay (SMP): whether an employee's earnings qualify, and the
39 weekly amounts that follow.

- Weeks 1 to 6: **90% of average weekly earnings** (AWE), with no cap.
- Weeks 7 to 39: the **lower of 90% of AWE and the flat weekly rate** in force.
- Every payment is **rounded up** to the next penny (SMP (General) Regulations
  1986 reg 28). AWE itself is not rounded first (HMRC: "Do not round the
  figure up or down to whole pence"), so 90% of £123.45 is £111.105, paid as
  £111.11.

## Which date decides which figure

- **Expected week of childbirth** (EWC): the Sunday-to-Saturday week containing
  the due date on the MATB1 (SSCBA 1992 s.171 defines a week as starting on
  Sunday).
- **Qualifying week**: the 15th week before the EWC, i.e. the Sunday 105 days
  before the EWC begins.
- **Eligibility**: AWE must be at least the NI lower earnings limit that
  applies **at the end of the qualifying week** (its Saturday). A qualifying
  week ending on 11 April 2026 uses the 2026-27 LEL of £129 even though it
  started in 2025-26, when the LEL was £125.
- **Flat rate**: SMP weeks begin on the weekday the maternity pay period
  starts. Each week is paid at the flat rate in force on the **day that week
  starts**. Rates change on the first Sunday in April (2 April 2023, 7 April
  2024, 6 April 2025, 5 April 2026), a day before the other statutory payments,
  and the dated rows in `data/smp-rates.json` carry those exact dates.

## Not covered

The other qualifying conditions are the caller's to check: 26 weeks'
continuous employment into the qualifying week, being on the payroll in the
qualifying week, notice and medical evidence (MATB1). AWE is an input: work it
out over the relevant period as HMRC's guide describes. Births before the
qualifying week, part-week payments aligned to a payroll period, and
Statutory Paternity, Adoption and Shared Parental Pay are not modelled. The
start date is not checked against the earliest allowed start (11 weeks before
the EWC), because an early birth moves it.

A `history=current` build keeps only the rates in force and refuses older
dates rather than answering them with today's figures.

## Sources

- GOV.UK, "Statutory Maternity Pay and Leave: employer guide" (39 weeks, 90% for 6
  weeks, then the lower of the flat rate or 90%; eligibility): https://www.gov.uk/employers-maternity-pay-leave
- HMRC, "Work out your employee's payments for Statutory Maternity Pay"
  (qualifying week, LEL at the end of the qualifying week, do not round AWE, SMP
  weeks start on the first day of the pay period):
  https://www.gov.uk/guidance/statutory-maternity-pay-manually-calculate-your-employees-payments
- HMRC, "Rates and thresholds for employers" 2023 to 2024 through 2026 to 2027
  (flat rates £172.48, £184.03, £187.18, £194.32 and their start dates; LELs
  £123, £123, £125, £129): https://www.gov.uk/guidance/rates-and-thresholds-for-employers-2026-to-2027
  and the pages for the earlier years at the same address with the years changed.
- The Statutory Maternity Pay (General) Regulations 1986, reg 28 (rounding up):
  https://www.legislation.gov.uk/uksi/1986/1960/regulation/28
- The Social Security Benefits Up-rating Order 2026 (SI 2026/148), arts 1 and 9
  (£194.32 in force 5 April 2026): https://www.legislation.gov.uk/uksi/2026/148/made