A practical guide covering full-time, part-time, and irregular hours workers. Updated for the 2024 Working Time Regulations changes.
The calculation for full-time workers is straightforward. Under the Working Time Regulations 1998, every worker is entitled to 5.6 weeks of paid annual leave per year.
For someone working a standard 5-day week:
Formula
5 days × 5.6 weeks = 28 days
This 28-day figure is the statutory maximum — even if someone works 6 or 7 days per week, their statutory entitlement caps at 28 days (though employers can offer more in the contract).
Important:The 28 days can include bank holidays. Many UK employers offer "20 days + bank holidays" which equals 28 days total. Others offer 25 days plus bank holidays (33 days total) — but that's contractual, not statutory.
Sarah works Monday to Friday (5 days per week).
Statutory entitlement: 5 × 5.6 = 28 days per year
Her employer offers 20 days annual leave + 8 bank holidays = 28 days (meets the statutory minimum exactly).
Part-time workers are entitled to the same 5.6 weeks of holiday — calculated on a pro-rata basis. The formula is simple:
Formula
Days worked per week × 5.6 = Annual entitlement
Under the Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000, employers must not treat part-time workers less favourably. This means pro-rata holiday must be proportionally equivalent.
Tom works Tuesday, Wednesday, and Thursday (3 days per week).
Statutory entitlement: 3 × 5.6 = 16.8 days per year
His employer rounds up to 17 days. Bank holidays that fall on his working days are included.
The Employment Rights (Amendment, Revocation and Transitional Provision) Regulations 2023 introduced a simplified accrual method for irregular hours and part-year workers, effective from April 2024.
This applies to zero-hours contract workers, casual workers, term-time only staff, and anyone whose hours vary significantly from week to week.
New Accrual Rate
Hours worked × 12.07% = Holiday accrued
(12.07% = 5.6 weeks ÷ 46.4 working weeks)
The 12.07% figure comes from dividing the 5.6-week statutory entitlement by 46.4 weeks (52 weeks minus 5.6 weeks of holiday). Holiday accrues at the end of each pay period.
Priya works on a zero-hours contract. In January, she works 80 hours.
Holiday accrued: 80 × 12.07% = 9.66 hours
If she's paid £12/hour, her holiday pay for that period = 9.66 × £12 = £115.92
David is a teaching assistant who works 39 weeks per year, 30 hours per week.
Total hours per year: 39 × 30 = 1,170 hours
Holiday accrued: 1,170 × 12.07% = 141.2 hours (equivalent to 4.7 weeks at 30 hours)
When someone joins or leaves partway through the leave year, you need to calculate their pro-rata entitlementbased on the proportion of the year they've worked.
Formula for Mid-Year Starters
(Annual entitlement ÷ 12) × complete months remaining = Pro-rata days
Alternatively, you can calculate based on the exact number of days: (annual entitlement ÷ 365) × days remaining in the leave year.
Company leave year runs January to December. Alex starts on 1 July (full-time, 5 days/week).
Full annual entitlement: 28 days
Months remaining: 6 (July to December)
Pro-rata: (28 ÷ 12) × 6 = 14 days
Megan resigns on 31 March. Leave year runs January to December.
Months worked: 3
Accrued entitlement: (28 ÷ 12) × 3 = 7 days
If she's taken 10 days, the employer can deduct 3 days' pay from her final salary (if the contract allows). If she's only taken 4 days, she's owed 3 days' holiday pay.
From April 2024, rolled-up holiday pay is explicitly legal for irregular hours and part-year workers. This means employers can add a 12.07% supplement to every payslip instead of tracking accrued days separately.
Previously, rolled-up holiday pay existed in a grey area — technically not compliant with EU law but widely used in practice. The 2024 regulations formalised it for qualifying workers.
Jake works irregular shifts at a warehouse. In February, he earns £2,000 gross.
Holiday pay supplement: £2,000 × 12.07% = £241.40
His payslip shows: Base pay £2,000 + Holiday pay £241.40 = Total £2,241.40
These errors frequently lead to tribunal claims and back-pay calculations. Get them right from the start.
Not including bank holidays in the calculation
Remember: 28 days can include bank holidays. If you give 20 days + bank holidays, you're meeting the minimum exactly.
Rounding down part-time entitlement
Always round up (or to the nearest half day). Rounding down risks falling below statutory minimums.
Using 12.07% for regular part-time workers
The 12.07% accrual method is only for irregular hours and part-year workers. Regular part-timers use the days × 5.6 formula.
Not pro-rating bank holidays for part-timers
If full-timers get 8 bank holidays, a 3-day worker should get 4.8 (round to 5). Don't just give them the bank holidays that fall on their working days.
Forgetting holiday accrues during sick leave
Statutory holiday continues to accrue during sickness and maternity. Build in carry-over provisions for these scenarios.
Using a use-it-or-lose-it policy without safeguards
Under the Kreuziger ruling, you must actively encourage workers to take holiday. If you haven't, they may be able to carry it forward indefinitely.
Manually calculating holiday entitlement for every employee — especially with a mix of full-time, part-time, and irregular workers — is time-consuming and error-prone.
Offly handles it automatically. When you add an employee and set their working pattern, entitlement is calculated correctly from day one. Mid-year starters, part-time schedules, and carry-over rules are all handled without spreadsheets.
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Offly handles entitlement calculations, pro-rata adjustments, and accrual tracking automatically. Free for up to 5 users.