Step 1: find the qualifying week
The qualifying week is the 15th week before the week the baby is due. It anchors everything: you need 26 weeks' continuous service ending with it, and your average weekly earnings are measured in the 8-week relevant period ending with your last payday before it ends. A pay rise that lands after the relevant period does not raise your SMP, however generous — and a bonus paid inside the window does count, which is why the timing of a bonus can change the first 6 weeks' pay substantially.
Step 2: work out average weekly earnings
Add up all gross pay in the relevant period — salary, overtime, commission and bonuses — and divide by 8 (or by the number of weeks actually paid, if you were paid for fewer). For monthly-paid staff, two monthly payslips in the window are divided by 2 and then by 4.33 to reach a weekly figure. The result must be at least £129 a week, the 2026/27 lower earnings limit, or there is no SMP at all.
Step 3: apply the two-stage formula
| Weeks | Weekly SMP (2026/27) |
|---|---|
| Weeks 1–6 | 90% of average weekly earnings, no cap |
| Weeks 7–39 | Lower of £194.32 or 90% of average weekly earnings |
| Weeks 40–52 | No SMP — leave continues unpaid unless your employer tops it up |
Two worked examples
Higher earner: £36,000 a year is £692.31 a week, so 90% is £623.08. Weeks 1–6 pay £623.08 a week (£3,738.46), then weeks 7–39 pay the flat £194.32 (£6,412.56) — £10,151.02 over 39 weeks, before tax and National Insurance. Lower earner: £180 a week gives 90% of £162, which is below the flat rate, so all 39 weeks pay £162 — £6,318 in total. The crossover point is £215.91 a week: earn above it and the flat rate bites from week 7; earn below it and 90% applies throughout.
What employers can reclaim, and what to watch
Employers pay SMP and usually reclaim 92% from HMRC; small employers (those whose National Insurance bill was £45,000 or less in the previous year) reclaim 103% plus compensation. For employees, the watchpoints are the notice deadline (28 days before SMP is due to start), keeping-in-touch days (up to 10, paid by agreement, without ending leave), and the fact that SMP stops if you return to work — the remaining leave is lost, not banked. Contractual maternity pay, if your employer offers it, usually includes SMP within it rather than adding to it, so read the policy before assuming a top-up.
Run your own figures with the maternity pay calculator, and for the tax treatment see is maternity pay taxed.