If you are an irregular hours or part-year worker, your holiday builds up at 12.07% of the hours you actually work in each pay period. Work 70 hours in a month and you accrue 8 hours of paid leave.
That rule applies to leave years beginning on or after 1 April 2024. Before then, a different and more generous calculation applied to some workers, which is why older advice online often disagrees with this.
A year is 52 weeks. Take off 5.6 weeks of leave and 46.4 working weeks remain. 5.6 divided by 46.4 is 12.07% — the accrual rate for irregular hours.
Where 12.07% comes from
It is not an arbitrary figure. Every worker in the UK is entitled to 5.6 weeks of paid holiday. Take 52 weeks in a year, subtract those 5.6 weeks of leave, and 46.4 working weeks remain. 5.6 divided by 46.4 is 12.07%.
So the percentage is just 5.6 weeks expressed as a proportion of the time you are actually at work. Someone working full time all year and someone on a zero hours contract end up with proportionally the same entitlement — one gets it as weeks, the other accrues it hour by hour.
The part that actually matters: are you an irregular hours worker?
This is the question that decides everything, and it is not a maths question. It is a question about what your contract says.
You are an irregular hours worker if the paid hours you work in each pay period are, under your contract, wholly or mostly variable.
You are a part-year worker if you are contracted to work only part of the year and there are periods of at least a week during which you are not paid — term-time-only staff being the clearest example.
Two things worth being direct about:
There is no numerical threshold in the legislation. No percentage of variation tips you from one category to the other. “Wholly or mostly variable” is a judgement about your contract, and the boundaries have not yet been tested extensively.
Rotating shifts and annualised hours do not automatically count. If you work a rota that changes week to week but your total contracted hours are fixed, you are probably not an irregular hours worker. The variation has to be in the paid hours themselves, not just in when you work them.
Getting this wrong is the real risk. The arithmetic is trivial; the classification is where people lose money.
A worked example
Someone on a zero hours contract works 70 hours in June.
- 70 hours × 12.07% = 8.449 hours
- Rounded to whole hours: 8 hours of paid holiday accrued
Run this example in the holiday calculator
The rounding rule
Accrual is worked out per pay period, and part hours are rounded: down below 30 minutes, up at 30 minutes or more.
This is not conventional rounding to the nearest hour applied once a year. It happens every pay period, which means the same annual hours can produce a slightly different total depending on how often you are paid. That is a feature of the rules, not an error in anyone’s calculation.
Rolled-up holiday pay
For leave years starting on or after 1 April 2024, employers in Great Britain may pay irregular hours and part-year workers an extra 12.07% on top of each payslip instead of paying holiday when it is taken. This is called rolled-up holiday pay, and it was previously unlawful.
Two conditions: it must be itemised separately on your payslip, and it applies only to irregular hours and part-year workers. It cannot be used for a regular hours employee.
Rolled-up holiday pay cannot be used in Northern Ireland. The 2023 Regulations that permit it extend to Great Britain only. In Northern Ireland, holiday pay must still be paid when the leave is actually taken.
Being paid rolled-up holiday pay does not remove your right to take the time off. You are still entitled to the leave; you have simply already been paid for it.
Why older guidance disagrees
Between 2022 and 2024 a different rule applied, following the Supreme Court’s decision in Harpur Trust v Brazel. That case concerned a part-year music teacher and established that her holiday could not be pro-rated using the 12.07% method — she was entitled to 5.6 weeks based on her average earnings, which produced a more generous result for people working few weeks a year.
The 2023 Regulations reversed that effect for leave years beginning on or after 1 April 2024. Guidance written between those dates is not wrong for its time, but it does not describe the current position.
If you are calculating for a leave year that began before 1 April 2024, the older method still applies to that year.
Northern Ireland
The position in Northern Ireland differs, and sources disagree about how much.
Rolled-up holiday pay is clearly not permitted there. Whether the 12.07% accrual method was mirrored in Northern Ireland legislation is less clear — some sources state it was, others note the 2023 Regulations extend to Great Britain only and that Northern Ireland may still follow the Harpur Trust position.
If you work in Northern Ireland, treat any accrual figure as indicative and check with the Labour Relations Agency before relying on it. We would rather say this plainly than pick an interpretation and present it as settled.
What to do if you think your holiday is wrong
- Check your contract for how your hours are described. That determines your category.
- Check your payslip for a separately itemised holiday pay line, which indicates rolled-up pay.
- Ask your employer which method they are using and why. They should be able to tell you.
- If you disagree, Acas provides free advice.
Sources
- Holiday entitlement for irregular hours and part-year workers — Acas
- The Employment Rights (Amendment, Revocation and Transitional Provision) Regulations 2023 — legislation.gov.uk
- Holiday entitlement — GOV.UK
Checked against source on 30 August 2026. This is general guidance, not legal advice.
Written by Nathan Cole
I built the calculators on HoursHQ and check every statutory figure against GOV.UK, Acas and the legislation itself before it goes live. Where the law is genuinely unclear, I say so rather than guessing.