How To Calculate Annual Leave For Employees In The UK

Getting annual leave right is one of those admin jobs that can either be smooth and stress-free… or a source of constant disputes and payroll headaches.

The good news: once you understand the rules in the Working Time Regulations and set up a clear policy, it’s straightforward to calculate annual leave for full-time, part-time, irregular hours and seasonal staff.

In this guide, we’ll walk you through how to calculate holiday accrual, how to handle starters and leavers, what to include in holiday pay, and common pitfalls to avoid. We’ll also flag where the rules have changed for irregular and part-year workers from April 2024, so you’re confidently compliant from day one.

What Is Statutory Annual Leave And Who Gets It?

Under the UK Working Time Regulations 1998, most workers are entitled to at least 5.6 weeks’ paid annual leave each leave year. For someone who works five days a week, that’s 28 days. You can offer more by contract, but you can’t offer less.

Key points to keep in mind:

• “Worker” has a broad definition. This generally includes employees and most casual/zero-hours workers. If you’re unsure how to classify someone, get clarity early - it affects holiday rights, Zero-Hour Contracts, and other protections.
• Bank holidays aren’t a separate statutory entitlement. You can choose to include them within the 5.6 weeks or offer them on top - the contract should say which approach you take.
• Statutory leave is split into two parts for pay purposes: 4 weeks (often called “Reg 13 leave”) and 1.6 weeks (“Reg 13A leave”). The 4 weeks must be paid at “normal remuneration” (see Holiday Pay below), while the 1.6 weeks can be paid at basic rate unless you choose to enhance it.
• From April 2024 leave years, the rules for irregular-hours and part-year workers were updated. For these groups you can again accrue statutory leave at 12.07% of hours worked and, in specific cases, use rolled-up holiday pay lawfully (details below).

Before we dive into the maths, make sure your Employment Contract and Staff Handbook spell out your leave year, how leave is requested/approved, whether bank holidays are included, and how carry-over works. Clear wording avoids most disputes.

How To Calculate Annual Leave For Different Working Patterns

Your approach depends on the working pattern. Here’s a simple framework you can apply across your workforce.

1) Full-Time Staff (Fixed Days Per Week)

For someone working five days each week, statutory leave is 5.6 weeks x 5 days = 28 days.

If they work a standard five-day pattern but different daily hours, you can calculate in hours instead of days. For example, 5.6 weeks x total weekly hours. So if they work 37.5 hours a week, statutory leave is 5.6 x 37.5 = 210 hours per leave year.

2) Part-Time Staff (Fixed Days Or Hours)

Part-time workers receive the same 5.6 weeks on a pro-rata basis. Two common methods:

• By days: If they work 3 days per week, 5.6 x 3 = 16.8 days.
• By hours: If they work 20 hours per week, 5.6 x 20 = 112 hours.

Hours-based entitlement is usually the most accurate where daily hours vary.

3) Irregular-Hours Or Zero-Hours Workers

For irregular-hours and part-year workers, reforms applying to leave years starting on or after 1 April 2024 allow statutory leave to accrue as a percentage of hours worked in the pay period. The standard rate is 12.07% (which equates to 5.6 weeks out of 46.4 working weeks when the 5.6 weeks of leave are excluded from the working year).

How it works in practice:

• In each pay period, multiply hours worked by 12.07% to accrue holiday.
• Record accrued hours on your payslip/HRIS so staff can see their running balance.
• Leave is then taken and deducted in hours, based on their typical working patterns/rotas.

For true casual patterns or variable rotas, this rolling accrual is usually the most practical. It also aligns with the latest legal position for these categories, replacing the post–Brazel uncertainty for term-time workers. If you engage people on very flexible arrangements, double-check your agreements and your approach to Zero-Hour Contracts to ensure your policies and payroll processes match the new rules.

4) Shift Workers And Hourly Calculations

Where staff work shifts of different lengths, calculate and book leave in hours. For example, if an employee typically works three 8-hour shifts and one 4-hour shift in a week (28 hours total), their statutory entitlement is 5.6 x 28 = 156.8 hours per leave year (or use 12.07% accrual if they’re irregular hours).

5) Including Bank Holidays

You can either:

• Include bank holidays within the 5.6 weeks and require staff to take leave on those days if your business closes, or
• Offer bank holidays on top of 5.6 weeks as a contractual enhancement.

Whichever you choose, make it clear in contracts and policy. If you include bank holidays within the 5.6 weeks and your rota covers weekends, you’ll typically provide a pro-rata number of days or hours for part-time staff to keep things fair.

Starters, Leavers And In-Year Changes: Pro Rata And Accrual

Most leave issues pop up when people join, leave, or change hours mid-year. Here’s how to avoid the common traps.

New Starters

For fixed-hours staff, pro-rate their annual entitlement based on the portion of the leave year they work. Example: if your leave year is 1 January–31 December and someone joins on 1 April (i.e., 9 months left), they get 9/12 of the full-year entitlement.

During the first year of employment, you can also use monthly accruals (e.g., 1/12 per completed month). Just make sure your policy is consistent and clearly communicated.

Leavers

On termination, calculate how much leave they’ve accrued up to their leaving date and compare it to what they’ve taken:

• If they’ve taken less than accrued, pay them for the untaken balance.
• If they’ve taken more than accrued, you can usually make a deduction from final pay, provided your contract and policy allow it and the deduction is lawful. See the rules on Wage Deductions.

Changing Hours Mid-Year

If someone moves from full-time to part-time (or vice versa), split the leave calculation:

• Work out what they accrued under the old pattern up to the change date.
• Then calculate on the new pattern for the rest of the leave year.

Keep records showing the date of the change and the calculation method - it’s one of the most common areas where misunderstandings arise.

Accrual During Absence

Workers continue to accrue statutory annual leave during maternity, paternity, adoption and shared parental leave. They also accrue during paid sick leave, and case law allows carry-over of the 4 weeks where a worker couldn’t take leave due to sickness. If long-term absence is relevant in your team, review your policy and consider how it interacts with Long-Term Sick Pay and scheduling when the employee returns.

Holiday Pay: What Should You Pay When Staff Take Leave?

Pay for annual leave must reflect a worker’s “normal remuneration,” not just basic pay, for their core 4 weeks of statutory leave. That typically includes:

• Basic salary or hourly pay
• Regular overtime that’s intrinsically linked to the job
• Regular commission payments
• Regular allowances intrinsically linked to the performance of the duties

For the additional 1.6 weeks’ statutory leave, you can lawfully pay basic pay only (unless your contract provides otherwise). Many employers choose to pay all leave at normal remuneration to keep things simple and reduce the risk of underpayments.

If your team regularly works extra hours, sense-check your approach against your policy on Overtime. Holiday pay calculations that ignore regular overtime or commission are a common source of claims.

Rolled-Up Holiday Pay (Irregular/Part-Year Workers)

For leave years beginning on or after 1 April 2024, you may use rolled-up holiday pay for irregular-hours and part-year workers. This allows you to pay an uplift (typically 12.07%) on top of pay for work done in each pay period, rather than paying when leave is taken.

If you use this method:

• State it clearly in contracts and payslips as a separate element.
• Make sure the percentage aligns with statutory rules and your leave policy.
• Remember workers must still be able to take time off - rolling up pay doesn’t remove the right to take leave.

How To Treat Commission And Bonuses

Where commission is a regular part of normal pay, include it in the holiday pay reference period calculation (usually averaging over 52 paid weeks, excluding weeks without pay). Discretionary one-off bonuses are less likely to count, but regular, intrinsically linked payments should be included.

Bank Holidays, Carry-Over And Common Pitfalls

Here are the policy decisions and day-to-day issues that tend to cause friction - plus how to handle them confidently.

Bank Holidays

If your business closes on bank holidays and you include those days within the 5.6 weeks, your contracts should say so. For part-time staff who don’t work the day a bank holiday falls on, you’ll usually allocate a pro-rata bank holiday allowance in hours to keep treatment even-handed across different patterns.

Carry-Over

As a baseline, workers should be able to take their 5.6 weeks within the leave year. However, there are lawful carry-over scenarios:

• If your contract or policy allows limited carry-over (e.g., up to 1.6 weeks) with advance approval.
• Where a worker couldn’t take the 4 weeks due to sickness or family leave - carry-over is permitted, with time limits (often up to 18 months for sickness-related carry-over).

COVID-era temporary carry-over rules have now expired for most cases, so make sure your policy reflects the current position.

Notice To Take Leave And Refusals

You can require employees to give notice to take leave, and you can refuse requests on reasonable business grounds. If you do refuse, offer alternative dates. A clear, consistent policy keeps decisions fair and reduces grievances.

Avoid These Common Mistakes

• Not specifying whether bank holidays are included in the 5.6 weeks - this causes confusion and payroll errors.
• Paying only basic pay for all leave where staff have regular overtime or commission - a risk for underpayment claims.
• Using day-based entitlements where shifts vary - hour-based accounting is far more accurate.
• For irregular-hours teams, forgetting the updated 12.07% accrual/rolled-up options from April 2024 - policy and payroll need to be aligned.
• Deducting overtaken holiday from final pay without a contractual right - ensure your contracts and policy allow lawful Wage Deductions.

A Step-By-Step Method To Calculate Annual Leave Accurately

Use this simple workflow to calculate holiday accrual and pay on any pay run:

1. Confirm the worker’s category and pattern. Fixed hours/days, part-time, irregular-hours or part-year? This drives your approach.
2. Set the unit of account. Use days for fixed daily patterns; hours for variable or shift-based patterns.
3. Calculate the statutory entitlement.
   • Fixed pattern: 5.6 x days per week, or 5.6 x weekly hours.
   • Irregular/part-year: accrue at 12.07% of hours worked each pay period (for leave years from April 2024).
4. Apply any contractual enhancement. If you offer more than 5.6 weeks, add that on top and reflect the higher entitlement in your system.
5. Adjust for starters/leavers/change of hours. Pro-rate by time served in the leave year and split calculations where patterns change.
6. Calculate holiday pay correctly. Use normal remuneration for 4 weeks and basic pay for 1.6 weeks (or enhance). Include regular overtime/commission where required.
7. Record balances and approvals. Keep clean records in your HR/payroll system and state decisions in line with your Staff Handbook.

As you embed this workflow, sense-check that your processes also reflect your wider obligations around working time limits and breaks under the Working Time Regulations.

What To Put In Your Contracts And Policies

The fastest way to avoid confusion is to make your documents crystal clear. At minimum, your Employment Contract and Staff Handbook should cover:

• Leave year start and end dates
• Whether 5.6 weeks includes bank holidays, or bank holidays are in addition
• How entitlement is calculated (days or hours), including for irregular-hours or part-year workers
• Approval process, notice requirements and how refusals are handled
• Carry-over rules and any caps or deadlines
• Holiday pay basis (normal remuneration vs basic, or any enhanced approach)
• Pro-rata rules for starters and leavers, and the right to make lawful final pay deductions for overtaken leave
• How policy interacts with overtime and variable pay, with a cross-reference to your Overtime and scheduling policy

It’s also good practice to explain, in plain language, how you calculate annual leave for different patterns and to provide worked examples. If you’re updating policies to reflect the April 2024 reforms for irregular-hours and part-year workers (e.g., 12.07% accrual and rolled-up holiday pay), signpost the change clearly and train managers on the new approach.

Worked Examples You Can Reuse

Example A: Part-Time, Fixed Days

Jane works 3 days per week all year. Statutory entitlement is 5.6 x 3 = 16.8 days. Your policy rounds to the nearest half day. She books 16.5 days. Bank holidays are included within the 16.8 days and must be taken if they fall on her normal working days.

Example B: Variable Shifts, Hours-Based

Mo works 28 hours per week on varied shift lengths. You account in hours. Statutory entitlement is 5.6 x 28 = 156.8 hours. He takes a week off and would normally have worked three 8-hour shifts and one 4-hour shift that week (28 hours), so you deduct 28 hours from his balance. Holiday pay is based on normal remuneration, using a 52-week reference period.

Example C: Irregular-Hours Worker (From April 2024 Leave Year)

Ada is on a zero-hours arrangement and works 90 hours in May. You accrue at 12.07%, so she accrues 10.863 hours in May (rounded per your policy). She later books a day off equivalent to her typical shift length, and you deduct that number of hours from her accrued balance. If you’ve opted for rolled-up holiday pay, you also pay a 12.07% uplift each pay period and clearly show it on the payslip.

Example D: Starter Mid-Year

Sam joins on 1 September. Your leave year runs 1 January–31 December. He works 5 days a week. Full-year entitlement is 28 days; pro-rata for 4 months is 28 x (4/12) = 9.33 days. Your policy rounds up to the nearest half day for fairness (9.5 days).

Compliance Tips To Keep Everything On Track

• Choose one calculation method per category and stick to it. If you move someone between categories (e.g., fixed to irregular), record the switch and adjust your approach accordingly.
• Document approvals and refusals. Consistency is your best defence against grievances.
• Check payroll configuration. Entitlement units (hours vs days), pay elements (normal remuneration) and carry-over caps should match your policy text.
• Review policies annually. If case law or regulations shift, refresh the wording and re-brief managers.
• Keep an eye on wider working time compliance - rest breaks, weekly limits and night work - as leave interacts with scheduling. If in doubt, revisit the Working Time Regulations.

Key Takeaways

• Statutory annual leave is at least 5.6 weeks per year. Use days for fixed patterns and hours for variable patterns to keep calculations accurate.
• From April 2024 leave years, irregular-hours and part-year workers can accrue at 12.07% of hours worked, and rolled-up holiday pay is permitted for these categories with the right safeguards.
• Holiday pay for the core 4 weeks must reflect normal remuneration - typically including regular overtime and commission - with 1.6 weeks at basic pay unless you enhance it.
• Pro-rate accurately for starters, leavers and mid-year changes, and only make final pay deductions for overtaken leave if your contract and policy allow lawful Wage Deductions.
• Be explicit in your Employment Contract and Staff Handbook about bank holidays, carry-over, approval rules and how you calculate annual leave.
• Align your approach to leave with your policies on Overtime, the Working Time Regulations, and treatment during Long-Term Sick Pay.

If you’d like tailored help setting up watertight contracts and policies - or a quick review of your holiday pay calculations - our team can help. You can reach us on 08081347754 or team@sprintlaw.co.uk for a free, no-obligations chat.