The SMP qualifying week explained
The qualifying week is the 15th week before the week a baby is due, and it is the single date that decides almost everything about Statutory Maternity Pay [2]. It fixes whether an employee has enough service, whether their earnings are high enough, and whether the employer can claim 109% rather than 92% when reclaiming the cost [10]. Get this one week wrong and every figure that follows is wrong too.
For an employer, identifying the qualifying week is the first practical task once a pregnancy is confirmed. It is a fixed point counted backwards from the due date, not a date the employee or employer can choose.
This article explains what the qualifying week is, how to work it out, why it matters for eligibility and pay, how it sets the relevant period for average weekly earnings, and what happens when a baby arrives early.
Key takeaways
- The qualifying week is the 15th week (Sunday to Saturday) before the expected week of childbirth.
- It is found by counting back 15 Sundays from the Sunday of the week the baby is due.
- The 26-week continuous employment test runs into the qualifying week.
- Average weekly earnings are tested at the end of the qualifying week against the £129 Lower Earnings Limit.
- If the baby is born early, special rules adjust the relevant period.
What the qualifying week is
The expected week of childbirth (EWC) is the week, starting on a Sunday, in which the baby is due [2]. The qualifying week is the 15th week before that EWC, again running Sunday to Saturday [3]. It is a single seven-day week, not a flexible window.
The qualifying week exists because SMP needs a fixed reference point that does not move with the employee's choices about when to start leave [1]. Every eligibility test and the average-earnings calculation hang off it [8]. Modern HMRC-recognised payroll software for SMEs derives the qualifying week automatically once the due date is entered.
How to work out the qualifying week
The method is a backward count from the due date. An employer takes the Sunday of the expected week of childbirth and counts back 15 Sundays, not including the Sunday of the EWC itself [1]. That 15th Sunday is the first day of the qualifying week [2].
As an illustration, if the expected week of childbirth begins on Sunday 5 October, the qualifying week is the seven days beginning on the Sunday 15 weeks earlier, which is the week starting Sunday 22 June. HMRC's maternity calculator for employers performs the same count and also returns the relevant period and average weekly earnings [9]. The due date comes from the MATB1 certificate, which is why collecting that evidence early is part of the wider set of employer maternity pay obligations [3].
Why the qualifying week matters
The qualifying week is the anchor for the two eligibility tests an employer must run. Both tests are measured against it, so a misidentified week can wrongly grant or deny SMP.
The continuous employment test
To qualify for SMP, an employee must have been continuously employed by the same employer for at least 26 weeks ending with the qualifying week [8]. Because the qualifying week is the 15th week before the due date, this means the employment must have started well before the pregnancy was confirmed [2].
If the 26 weeks of service are not complete by the qualifying week, the employee does not qualify for SMP, regardless of how long they work afterwards [8]. The employer then issues form SMP1 so the employee can pursue Maternity Allowance instead [2].
The earnings test
The employee's average weekly earnings must be at least the Lower Earnings Limit, which is £129 a week for the 2026-27 tax year, measured at the end of the qualifying week [7]. The relevant Saturday at the end of the qualifying week is the date on which that limit is applied [1].
The qualifying week also decides Small Employers' Relief, because the £45,000 National Insurance test looks at the last complete tax year before the qualifying week [10]. That link feeds straight into reclaiming SMP from HMRC at the higher 109% rate [10].
The relevant period for average weekly earnings
Average weekly earnings are not measured during the qualifying week itself but over a relevant period that ends near it. The relevant period is usually the 8 weeks ending with the last normal payday on or before the Saturday of the qualifying week [5]. The start of the relevant period is the day after the last payday falling at least 8 weeks before that end point [5].
To find the average, the employer adds up all the earnings subject to Class 1 National Insurance paid in the relevant period and divides by the number of weeks or months in it [6]. Only earnings that attract Class 1 National Insurance count, so items outside National Insurance are excluded from the average [6]. The resulting figure drives both eligibility and the 90% higher rate paid in the first 6 weeks [4]. Platforms that embed an HMRC-recognised payroll API return the same average from the underlying engine, so the calculation is consistent wherever the payroll is run.
What happens if the baby arrives early
A baby born before the qualifying week does not remove the right to SMP, but it does change the calculation. Where the birth happens before or during the qualifying week, the relevant period for average weekly earnings is measured against the week the baby is actually born rather than the original due date [4].
An early birth can also bring the maternity pay period forward, because SMP starts automatically from the day after the birth if the baby arrives before the planned leave start [2]. An accountant payroll platform handling several clients recalculates the relevant period when the actual birth date is entered, which avoids a manual reworking of the average [4].
Conclusion
The qualifying week looks like a small administrative detail, but it is the hinge the whole SMP calculation turns on. It fixes the service test, the earnings test, the relevant period, and the Small Employers' Relief test, all from one date counted back from the due date.
Because so much depends on it, the qualifying week is worth identifying the moment the MATB1 confirms the due date, rather than at the point leave begins. An employer that pins the week down early has, in effect, already settled eligibility and the average-earnings basis, leaving only the payment and recovery to run.
Frequently asked questions
How do you calculate the SMP qualifying week?
Take the Sunday of the week the baby is due, the expected week of childbirth, and count back 15 Sundays without counting that first Sunday [1]. The 15th Sunday begins the qualifying week, which runs Sunday to Saturday [2]. HMRC's maternity calculator for employers works this out automatically from the due date [9].
Is the qualifying week the same as the relevant period?
No. The qualifying week is a single seven-day week, the 15th week before the due date, used for the eligibility tests [3]. The relevant period is the roughly 8-week stretch ending near the qualifying week, over which average weekly earnings are measured [5]. The two work together but are different spans of time.
What earnings count towards average weekly earnings?
Only earnings that are subject to Class 1 National Insurance contributions count towards the average [6]. The employer totals those earnings across the relevant period and divides by the number of weeks or months in it [6]. The result must be at least £129 a week for the 2026-27 tax year for the employee to qualify [7].
Does an early birth change the qualifying week?
The qualifying week is set by the original due date, but an early birth changes the relevant period used for average weekly earnings, which is then measured against the week the baby is actually born [4]. An early birth also starts the maternity pay period automatically from the day after the birth [2]. The right to SMP itself is not lost because of an early arrival.
Image prompt for Imagen (also in frontmatter)
Documentary still life, a paper wall calendar on an office desk with one week lightly circled in pencil, a MATB1-style form and a pen beside it, soft daylight from a window, mid-morning, palette of warm white, paper cream, oak, pale graphite grey, the calendar occupying the left two-thirds of the frame, shot on a Fujifilm X-T5 at 35mm f/2.8, photojournalism, gentle film grain, no AI artefacts, no warped text, landscape orientation 16:9.
