Holiday pay sounds straightforward until you move beyond the standard nine-to-five, Monday-to-Friday employee. The moment you hire a part-time sales assistant, a seasonal delivery driver on a zero-hours contract, or a term-time-only school administrator, the calculations become considerably more complex. For small business owners and their accountants, getting this wrong is costly: Employment Tribunal claims for unpaid holiday pay have risen year on year, and back-pay liability can stretch back two years under the Deductions from Wages provisions. This guide sets out the rules clearly, explains where employers most commonly stumble, and gives you a practical framework for getting it right.
The Legal Foundation: What UK Law Actually Requires
UK workers are entitled to a minimum of 5.6 weeks' paid holiday per year under the Working Time Regulations 1998. For a full-time worker doing five days a week, that works out to 28 days. Part-time workers receive the same entitlement on a pro-rata basis under the Part-Time Workers (Prevention of Less Favourable Treatment) Regulations 2000 — meaning you cannot simply award them fewer days without a proportionate adjustment.
A part-timer working three days a week is therefore entitled to 3 ÷ 5 × 28 = 16.8 days of paid holiday per year. Many employers round this up to 17 days as a matter of good practice; you may never round down. Where a worker's schedule changes week to week — think of a retail assistant with variable shift patterns — the calculation requires a different approach entirely.
It is also worth noting that the 5.6 weeks is a floor, not a ceiling. Your employment contracts may offer more generous terms, and if they do, those contractual rights take precedence.
Calculating Holiday for Variable-Hours and Zero-Hours Workers
Variable-hours workers — including those on zero-hours contracts, casual contracts, and agency arrangements — present the biggest calculation challenge. Until relatively recently, the standard method was to accrue holiday at a rate of 12.07% of hours worked. This figure is derived from the fact that 5.6 weeks is 12.07% of the remaining 46.4 working weeks in a year.
However, the Supreme Court's ruling in Harpur Trust v Brazel [2022] complicated matters for part-year workers (those who work for only part of the year, such as term-time staff). The Court held that the 12.07% method should not be used for part-year workers with permanent contracts, because it can result in holiday entitlement that is lower than the statutory 5.6 weeks.
The Government's response was the Employment Rights (Amendment, Revocation and Transitional Provision) Regulations 2023, which took effect from 1 January 2024 and introduced two significant changes:
- Irregular-hours and part-year workers now accrue holiday at 12.07% of hours worked in each pay period — restoring the accrual method for these specific categories going forward.
- Rolled-up holiday pay became lawful again for irregular-hours and part-year workers, provided the uplift is calculated at 12.07%, paid in each payslip, and shown as a separate, clearly identified amount.
For workers with a regular pattern (even if part-time), the traditional pro-rata method remains the correct approach. Always start by categorising your workforce accurately before choosing a calculation method.
What Counts as "Normal Pay" — The Most Overlooked Rule
One of the most expensive mistakes small employers make is paying holiday pay at basic pay only, ignoring other regular elements of a worker's remuneration. Following a series of Employment Tribunal and Employment Appeal Tribunal decisions — most notably Bear Scotland v Fulton and the cases that followed — and HMRC's own guidance, holiday pay must reflect a worker's normal remuneration. This includes:
- Regular voluntary overtime (not occasional one-off shifts)
- Guaranteed and non-guaranteed overtime
- Regular commission payments
- Shift allowances and unsociable hours premiums paid routinely
- Certain travel allowances that are genuinely linked to the work performed
To calculate the correct rate, employers should use a 52-week reference period, averaging the worker's actual pay over the 52 weeks prior to the holiday being taken (ignoring any weeks in which no pay was received, and going back up to 104 weeks to find 52 paid weeks). This reference period was enshrined in law by the Employment Rights (Employment Particulars and Paid Annual Leave) (Amendment) Regulations 2018.
For a worker whose pay genuinely varies — for example, a field sales representative earning a base salary plus monthly commission — this averaging approach captures the true value of their normal earnings. Paying them only the base salary during annual leave would be unlawful.
Record-Keeping: Your First Line of Defence
Accurate records are not just good admin practice — they are your primary defence if a worker brings a tribunal claim for unlawful deduction of wages. You should be recording:
- Hours worked each day, including any overtime
- Holiday days taken and the dates they fell on
- The pay rate applied to each period of holiday and how it was calculated
- Any rolled-up holiday pay shown separately on payslips
For small businesses managing payroll manually, this can quickly become unwieldy — particularly when staff numbers grow or shift patterns change frequently. Platforms like BizHub365 include built-in payroll tools that track RTI submissions, generate payslips, and support statutory payment calculations, making it far easier to maintain an audit trail without relying on fragmented spreadsheets. When holiday pay queries arise, having a single source of truth for payroll history is invaluable.
Practical Tips for Common Scenarios
To make this tangible, here are three scenarios UK small business owners frequently encounter:
The Part-Time Café Worker
A barista works Tuesday, Wednesday, and Thursday each week — 22.5 hours. Their holiday entitlement is 3 ÷ 5 × 28 = 16.8 days per year. Their holiday pay rate is their normal weekly pay divided by three (days worked), then multiplied by the number of days of holiday taken. If they earn £11.44 per hour, their daily rate is £11.44 × 7.5 = £85.80. A full week's holiday costs the business £257.40.
The Zero-Hours Retail Assistant
A worker on a zero-hours contract works varying hours each week across a busy clothing boutique. You use the 12.07% accrual method: for every hour worked, 7.24 minutes of holiday is accrued. The holiday pay rate is calculated using the 52-week average. If rolled-up holiday pay is used from 1 April 2024 onwards, the 12.07% uplift must appear as a distinct line on each payslip.
The Term-Time School Administrator
This worker has a permanent contract but only works 39 weeks per year. Under the post-2024 rules, holiday accrues at 12.07% of hours worked in each pay period. The 52-week average pay reference period applies when calculating the rate. Critically, you must not simply divide 5.6 weeks by 39 working weeks — this was the error that Harpur Trust v Brazel addressed.
Conclusion: Stay Compliant, Stay Confident
Holiday pay for part-time and variable-hours workers is a genuinely nuanced area of UK employment law, and the rules have shifted meaningfully in recent years. The core principles, however, are consistent: pro-rate entitlement fairly, use the correct calculation method for the worker's contract type, ensure holiday pay reflects normal remuneration rather than just basic pay, and keep meticulous records.
For small business owners already juggling operations, sales, and finances, the administrative burden of getting all this right is real. Building clean payroll processes from the outset — and using tools that automate record-keeping and payslip generation — removes much of that burden. Whether you manage a team of two or twenty-two, a clear system is far less expensive than a tribunal claim.