# 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
## Before you rely on this
**Not professional advice.** This capability calculates payroll figures from published rules. It is a software component for developers, not tax or legal advice. Rules change and every rate here has an effective date. Check that the dates cover your case. Verify results against the official sources listed above, and have a payroll specialist review how you use it, before anyone relies on the output. Provided "as is" under its licence, without warranty.
**Unreviewed.** This capability's implementations agree in every language and pass its published test vectors, which were worked out from the official sources cited. But no qualified payroll specialist has yet checked those vectors, or confirmed that the capability covers the cases it claims. Treat it as a draft. Do not use it for real people, money or decisions without your own expert review. Once a qualified reviewer signs off, this notice is replaced with their name, qualification and the date. Each new version needs fresh sign-off.
## Notices
Contains public sector information licensed under the Open Government
Licence v3.0 (https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/).
Legislation: Crown copyright and database right.
1.0.1 marks it unreviewed and adds its attribution notices (NOTICE). The code and the tests are unchanged.