What are irregular working hours and how do they work in the UK?

Irregular working hours are becoming increasingly common across the UK workforce. Many businesses now rely on flexible staffing models to manage changing demand, seasonal workloads, shift coverage, and hybrid working arrangements. As a result, employees may work different hours each week rather than following a fixed work time schedule. 

While irregular work schedules can provide flexibility for both employers and workers, they also create additional responsibilities around calculating hours worked, holiday entitlement, rest breaks, and payroll compliance. UK employers must still comply with the Working Time Regulations 1998 and ensure workers receive their legal entitlements regardless of how variable their schedules may be.

What are irregular working hours?

Irregular working hours refer to working arrangements where a worker's paid hours vary from one pay period to another rather than following a fixed pattern. An irregular hours worker is someone whose number of paid hours in each pay period is wholly or mostly variable.

Are irregular hours the same as zero-hours contracts?

Irregular working hours and zero-hours contracts are not always the same.  Irregular hours workers usually include people on zero-hours contracts, casual contracts or bank contracts (ACAS). 

What counts as an irregular work schedule?

An irregular work schedule can include rotating shifts, casual work, variable weekly hours, split shifts, on-call arrangements, or contracts where hours change frequently. 

What are the laws that apply to irregular working hours in the UK?

Irregular working hours are regulated by several areas of UK employment law, including the Working Time Regulations 1998, National Minimum Wage legislation, and holiday entitlement rules. Employers must ensure workers receive the correct legal protections even when schedules change.

What does the Working Time Directive do?

The Working Time Directive introduced minimum standards for working hours, rest breaks, and annual leave. In the UK, these protections are reflected in the Working Time Regulations 1998, which continue to govern working time rights for many workers. 

What are the legal limits on working hours?

In most cases, workers’ maximum working hours are limited to an average of 48 hours per week, unless they voluntarily opt out (if over 18). 

Workers are also generally entitled to:

• An uninterrupted rest period of at least 24 hours in each seven-day period.

• A rest break of at least 20 minutes when the working day exceeds six hours.

What changes are coming under the Employment Rights Act 2025?

The Employment Rights Act 2025 introduces new protections for zero-hours and low-hours workers, expected to take effect from 2027 following consultation. Employers will need to offer eligible workers guaranteed hours based on a reference period of hours regularly worked, give reasonable notice of shifts, and pay for shifts cancelled or curtailed at short notice. Reviewing scheduling practices now will reduce the operational impact when the rules commence.

How is holiday entitlement calculated for irregular hours workers?

Holiday entitlement for irregular hours workers is usually calculated based on the number of hours worked rather than fixed working days. New UK rules introduced for leave years beginning on or after 1 April 2024 allow employers to use an accrual system for eligible workers (ACAS). 

What is the 12.07% holiday accrual method?

The 12.07% accrual method allows employers to calculate holiday entitlement as 12.07% of the hours worked during a pay period. This method is commonly used for irregular hours and part-year workers.

📌 Example: an irregular hours worker who completes 100 hours in a monthly pay period accrues 12.07 hours of holiday using the 12.07% method (100 × 12.07% = 12.07 hours), rounded to 12 hours of paid leave for that month.

Can holiday leave be carried over?

In some situations, holiday entitlement for irregular hours workers can be carried forward into the next leave year, for example when they are unable to take leave because of sickness, family leave, or if the employer failed to provide the opportunity to take holiday. 

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What is rolled-up holiday pay?

Rolled-up holiday pay is a system where holiday pay is added directly onto a worker’s hourly rate instead of being paid when leave is taken. This approach became lawful again for eligible irregular hours and part-year workers from April 2024.

How should rolled-up holiday pay appear on payslips?

Employers must clearly show rolled-up holiday pay as a separate item on payslips. The payment should be calculated accurately and workers must still be encouraged to take annual leave.

What are the risks of incorrect holiday calculations?

Incorrect holiday pay calculations can lead to problems with wages. Employers should calculate holiday pay carefully to ensure workers receive their full statutory holiday entitlement and holiday pay. HMRC can investigate underpayment of wages, and HMRC enforcement’s notices may require repayment of arrears and impose financial penalties where National Minimum Wage breaches are found.

What happens if an irregular hours worker takes leave or is sick?

Workers with irregular schedules may still be entitled to statutory rights such as Statutory Sick Pay, Statutory Maternity Pay, Statutory Paternity Pay, provided they meet the relevant employment status requirements and, where applicable, the earnings threshold, usually at least the Lower Earnings Limit set by HMRC (GOV.UK). 

Can irregular workers receive Statutory Sick Pay?

Yes. From 6 April 2026, Statutory Sick Pay rules changed in ways that significantly benefit irregular hours workers. The Lower Earnings Limit was removed, meaning part-time, low-paid and casual workers now qualify regardless of weekly earnings. SSP is also payable from the first day of sickness (the three "waiting days" have been removed).

For 2026/27, SSP is the lower of 80% of average weekly earnings or £123.25 per week, paid for up to 28 weeks (Acas, 8 April 2026).

Does family leave apply to flexible workers?

Yes. Regular hours workers and part-year workers may still be entitled to statutory leave. Other leave might include maternity leave, paternity leave, adoption leave, shared parental leave, and parental leave, depending on their employment status.

What are the best practices for employers managing irregular working hours?

Managing irregular working hours well rests on three pillars: accurate time tracking, robust record-keeping, and clear communication with workers. Getting each one right protects employers from disputes, underpayment claims, and HMRC investigations, while giving workers visibility over their hours and pay.

How can businesses calculate employee hours accurately?

Businesses should track every shift, break and hour worked using a reliable method such as electronic rota software, digital timesheets or payroll and HR software. Good systems automatically calculate overtime, accrue holiday at the 12.07% rate, and check National Living Wage compliance for each pay period, flagging anomalies before payroll is processed.

What records must employers keep from April 2026?

From 6 April 2026, employers must keep records of annual leave and holiday pay, including any carried-over leave, for at least 6 years. For irregular hours workers, this means logging hours accrued at the end of each pay period and retaining payslip evidence of any rolled-up holiday pay. The same logic applies to weekly working time records under the Working Time Regulations 1998, which must be detailed enough to show the 48-hour weekly average has not been exceeded.

⚠️ Warning: Failure to keep adequate records can leave employers unable to prove compliance with the Working Time Regulations. This may trigger HMRC enforcement action, backdated pay claims, tribunal disputes, and financial penalties of up to 200% of arrears, capped at £20,000 per worker, for National Minimum Wage breaches. From April 2026, the new Fair Work Agency also has enforcement powers over Statutory Sick Pay and other core worker rights.

How should employers communicate variable schedules to workers?

Workers should know in advance how their hours, holiday entitlement and pay are calculated, particularly when shifts change between pay periods. Best practice includes publishing rotas with reasonable notice, sharing a written explanation of how the 12.07% accrual method applies to their pay, and giving each worker access to their accrued leave balance through a payroll or HR system. Clear, written communication reduces disputes and supports compliance with workers' right to be informed of their working patterns under the Employment Rights Act 2025.

What rules apply to night shift workers?

Night workers must not work more than an average of 8 hours in every 24-hour period, normally calculated over a 17-week reference period (extendable to 52 weeks by collective agreement).

Employers must also offer a free health assessment before someone starts night work and at regular intervals afterwards. Workers who deal with special hazards, or whose role involves significant mental or physical strain, must not work more than 8 hours in any 24-hour period (the average does not apply).