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Holiday accrual is one of those topics that sounds simple — 5.6 weeks for a full-time worker, scale it down for part-timers — and is anything but, once you start handling irregular hours, mid-year starters, sickness and parental leave. It is also one of the highest tribunal-risk areas for UK SMEs, because errors compound quietly and surface only when a worker leaves and the final calculation is challenged.

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This guide explains how holiday accrual actually works in the UK, where the edge cases live, and how to track it cleanly. Pair it with the right HR software and time and attendance records and most of the complexity disappears.

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The basics: 5.6 weeks for a full-time worker

The Working Time Regulations entitle a worker to a minimum of 5.6 weeks of paid holiday a year. For a full-time worker on a five-day week, that is 28 days. Many employers offer more — but 5.6 weeks is the floor below which contracts cannot legally go.

Bank holidays may be included within the 5.6 weeks or be additional, depending on the contract. Either is permitted; the contract should be explicit about which.

Part-time workers

Part-time workers are entitled to the same 5.6 weeks, calculated proportionally to their hours. A worker on three days a week is entitled to 5.6 × 3 = 16.8 days a year (or the equivalent in hours).

The Equality Act and the Part-Time Workers Regulations require pro-rata fairness on holiday — so part-timers must not be treated less favourably on accrual, on requests or on pay.

Irregular-hours and part-year workers

This is the area that has changed most in recent UK regulation. For workers whose hours are irregular, or who only work part of the year, statutory holiday accrues at 12.07% of hours actually worked in each pay period. So a worker who completes 30 hours in a week accrues approximately 3.62 hours of holiday for that week.

Employers can choose to pay this accrual either as it is taken or, in narrowly defined cases, as a 12.07% " rolled-up" uplift on each pay packet. Where rolled-up holiday pay is used, the rules are strict — see our guide to UK holiday pay for the detail.

Mid-year starters and leavers

For workers who start or leave part-way through the holiday year, entitlement accrues proportionally to the period they were employed. The standard formula:

Days worked in year ÷ 365 × annual entitlement = entitlement for the partial year.

For leavers, accrued but untaken holiday must be paid in lieu in the final salary. Untaken holiday cannot generally be paid in lieu while the worker is still employed (except for any contractual extra above the statutory minimum).

Holiday accrual during absence

Holiday continues to accrue while a worker is on sick leave, maternity leave, paternity leave, adoption leave, parental leave and shared parental leave. Workers do not lose entitlement just because they were absent — and any holiday they could not take because of long-term sickness can typically be carried forward.

Holiday pay calculation

Accrual is one half of the question; pay is the other. For variable-hours workers, holiday pay is calculated against the previous 52 weeks in which the worker was paid (excluding any week with no pay). Regular overtime, commission and shift premiums must be included where they are sufficiently regular.

This calculation is hard to do accurately by hand. Time and attendance data joined to a holiday module turns the 52-week reference period into a routine number rather than a quarterly exercise.

Carry-over rules

The default is that statutory holiday must be taken in the holiday year in which it accrues. Limited carry-over is permitted in narrow circumstances:

• Long-term sickness preventing the worker from taking leave.
• Family leave (maternity, paternity, etc.).
• Where the employer prevented the worker from taking leave.

Contractual holiday on top of the statutory minimum can be carried over by agreement between the parties.

Practical SME checklist

• State the holiday year clearly in every contract.
• State the entitlement (statutory + any contractual extra).
• State whether bank holidays are inside or on top.
• Identify each worker as regular, irregular-hours or part-year.
• Calculate accrual using the right method for each.
• Track requests, balances and carry-over in one place.
• Review the holiday balance per worker quarterly.

Common SME mistakes

Three patterns trip up most small employers:

• Treating part-timers' bank holidays unfairly when they fall on a non-working day.
• Underestimating accrual for irregular-hours workers (12.07% is the floor, not a target).
• Letting workers reach the end of the holiday year with significant unused balance and then disputing carry-over.

Each of these is solved by visibility — which is exactly what the right tooling provides. Annaizu's HR software shows accrual, taken, booked and remaining balance in one place, against the rota the worker actually worked.

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Conclusion

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Holiday accrual looks simple and behaves complicated. Get the basics right — clear contract, correct method per worker type, accurate pay calculation, visible balance — and the rest takes care of itself. Combine it with reliable rota, time and attendance and HR software, and holiday becomes a routine part of the operation rather than a quarterly fire drill.

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