Statutory Maternity Pay (SMP) is the minimum amount an employer must pay an employee during maternity leave. The calculation involves three steps: checking eligibility, working out the employee’s average weekly earnings, and applying the two-tier rate system — 90% of average earnings for six weeks, then a flat rate for the remaining 33 weeks. Errors in this calculation are among the most common payroll mistakes employers make.

This guide walks you through how to calculate maternity pay in the UK, including the current rates, eligibility criteria, and the step-by-step maths.

Key Takeaways

  • SMP runs for up to 39 weeks, paid in two tiers: 90% of average weekly earnings for six weeks, then £184.03 per week (or 90% if lower) for the remaining 33 weeks.
  • The employee must have been employed for at least 26 weeks by the end of the qualifying week (15 weeks before the expected week of childbirth).
  • Average weekly earnings are calculated over the 8-week period ending with the qualifying week.
  • SMP is subject to tax and National Insurance, unlike some other statutory payments.
  • Employers can offer contractual maternity pay above SMP.

Step 1: Confirm eligibility

The employee must meet all three conditions:

  1. 26 weeks’ employment — they must have been continuously employed for at least 26 weeks by the end of the 15th week before the expected week of childbirth (the qualifying week), under section 171 of the Employment Rights Act 1996.
  2. Earnings threshold — their average weekly earnings in the relevant 8-week period must be at least equal to the Lower Earnings Limit (currently £123 per week for 2025/26).
  3. Notice — the employee must give the correct notice, including the MAT B1 certificate from a doctor or midwife.

If any condition fails, the employee does not qualify for SMP. They may instead be eligible for Maternity Allowance from the Department for Work and Pensions.

Step 2: Calculate average weekly earnings (AWE)

The AWE is the key number because it determines both whether the employee qualifies and what they receive.

Formula:

AWE = Total gross pay in the 8-week qualifying period ÷ 8

The qualifying period is the 8-week period ending with the last payday before the end of the qualifying week (15 weeks before the expected week of childbirth).

Example: An employee’s gross pay in the 8 weeks was £3,200.

  • AWE = £3,200 ÷ 8 = £400 per week

If the employee was paid irregularly, use the pay period closest to the qualifying week.

Step 3: Apply the two-tier rate

SMP is paid in two phases:

Phase 1: 90% of average weekly earnings (first 6 weeks)

Weekly SMP (Phase 1) = AWE × 90%

Using the £400 AWE example: £400 × 90% = £360 per week for six weeks.

Phase 2: Flat rate or 90%, whichever is lower (weeks 7–33)

Weekly SMP (Phase 2) = The flat rate (£184.03) or 90% of AWE, whichever is lower

At £400 AWE, 90% is £360 — the flat rate of £184.03 is lower, so the employee receives £184.03 per week for weeks 7 to 33.

If the employee’s AWE is very low — say £200 — then 90% is £180, which is less than £184.03. They would receive £180 per week instead.

Step 4: Determine the payment period

SMP is paid for up to 39 weeks from the start of maternity leave:

  • 6 weeks at 90% of AWE
  • 33 weeks at the flat rate or 90% (whichever is lower)

The employee’s maternity leave starts on one of these dates (or up to 10 weeks before the expected week of childbirth if the baby arrives early):

  • The day after the baby is born
  • The first day of a qualifying week
  • A date specified in the notice

If the employee wants to take fewer than 39 weeks of SMP, they can stop claiming and return to work. The unused portion is lost.

Step 5: Check the contract for enhanced maternity pay

Many employers offer enhanced maternity pay above SMP. Common arrangements include:

  • Full pay for a fixed period, then SMP
  • Full pay for the entire 39 weeks
  • A sliding scale that reduces over time

Where contractual pay exceeds SMP, the employer pays the contractual amount and recoups the SMP through Section 66 orders or simply treats the contractual pay as inclusive. The statutory rate is the floor, not the ceiling.

Recovery of SMP from HMRC

Employers can recover 92% of SMP paid (or 103% for small employers). SMP is paid through payroll, so you are not making separate payments — you deduct the recovery amount through the standard payroll submission to HMRC.

Step 6: Handle early birth or complications

If the baby arrives before the expected week of childbirth:

  • Leave starts on the day after birth (even if the employee has not yet given notice)
  • SMP starts immediately if the employee qualifies — the qualifying period is the same
  • If the employee does not yet have a MAT B1, they can provide it as soon as they have it

If the employee is hospitalised or the baby requires neonatal care:

  • Additional leave and pay provisions apply under the Neonatal Care (Leave and Pay) Act 2024
  • Up to 12 weeks of additional leave and pay for neonatal care

Common maternity pay calculation errors

1. Using the wrong qualifying period

The AWE must be calculated from the 8-week period ending with the last payday before the qualifying week — not the 8 weeks before the due date.

2. Missing the 26-week employment check

Employment must have started at least 26 weeks before the end of the qualifying week. Start dates of zero-hours workers or those on irregular contracts need careful tracking.

3. Confusing the qualifying week with the start of leave

The qualifying week is 15 weeks before the expected week of childbirth. It is not the same as the start of maternity leave, and the earnings calculation does not extend to the start of leave.

4. Not adjusting for early birth

If the baby arrives early, the entitlement and the qualifying week calculations adjust automatically. Employers who do not account for this may miscalculate the AWE.

Putting it into practice

Five checks cover most maternity pay calculations:

  1. Confirm the employee has 26 weeks’ service by the qualifying week and earnings meet the threshold.
  2. Calculate AWE from the correct 8-week period ending before the qualifying week.
  3. Apply the 90% rate for six weeks, then the flat rate (or 90% if lower) for weeks 7–33.
  4. Check the contract for enhanced maternity pay and reconcile the contractual and statutory amounts.
  5. Handle early births by adjusting the qualifying period and SMP start date.
You can take advantage of the free 14 days trial and explore Leave Balance.

A leave management system that calculates SMP automatically, tracks the qualifying week, handles early births, and reconciles contractual enhancements against statutory rates removes the complexity from maternity pay.

Frequently Asked Questions

How much is statutory maternity pay?

For 2025/26, SMP is 90% of average weekly earnings for the first six weeks, then £184.03 per week (or 90% if that is lower) for the remaining 33 weeks.

When does SMP start?

SMP starts on the first day of maternity leave, which is usually the day after the baby is born, or a date chosen by the employee.

Can an employee get SMP and salary at the same time?

No. SMP replaces salary during maternity leave. Contractual maternity pay may be more generous than SMP, but the employee does not receive both salary and SMP.

What if the employee does not qualify for SMP?

If the employee does not meet the 26-week service or earnings threshold, they can claim Maternity Allowance from the Department for Work and Pensions.

How does early birth affect SMP?

If the baby arrives before the expected week, SMP still applies. The qualifying period adjusts to the last payday before the qualifying week relative to the actual birth date.

This article is general information, not legal advice.

Last updated: 26 July 2026.