Part-time, casual and zero-hours: where the hours decide the money

With salaried staff on fixed hours, a missing record is untidy. With hourly staff it is the difference between a correct payslip and a penalty of twice the shortfall.

Three calculations that all start with hours

• The hourly rate. Minimum wage compliance is pay divided by hours. Without the hours there is no denominator, and regulation 59(1) requires records "sufficient to establish" the rate.
• Holiday accrual. Since leave years beginning on or after 1 April 2024, regulation 15B gives irregular-hours and part-year workers 12.07% of the hours worked in each pay period, capped at 28 days.
• Rolled-up holiday pay. Regulation 16A allows a 12.07% uplift paid with wages, shown as its own line on the payslip — available only for these workers.

What that means in practice

1. Hours have to be recorded per pay period, not summed at year end, because that is the unit both calculations use.
2. They have to survive six years — regulation 59(8), raised from three in 2021.
3. They have to be defensible. Under the penalty regime in force since 7 April 2026, section 107 of the Employment Rights Act 2025 sets 200% of the underpayment per worker, with a £20,000 cap and a £100 floor.

A spreadsheet can hold all this. What it cannot do is show that a cell was not changed after the fact, which is exactly what is in dispute when it is in dispute.

What irot Time does with this

• Hours per person per pay period, with breaks separated, so the rate and the accrual both fall out of the same record.
• A running holiday balance the person can see, rather than a figure they have to ask for.
• An audit log on every correction: who, when, why, with the original kept.
• Export for payroll with premiums already calculated, and a monthly record to sign.

The part people forget

The rest break under regulation 12 depends on the length of the day, not the contract. A part-time worker doing a nine-hour Saturday is entitled to the same uninterrupted 20 minutes as anyone else, and a worker under 18 gets 30 minutes after four and a half hours. The limits in full.

Questions we get

How does holiday work for zero-hours staff?

For leave years beginning on or after 1 April 2024, regulation 15B accrues leave at 12.07% of the hours worked in each pay period, capped at 28 days a year. Regulation 16A also allows rolled-up holiday pay at 12.07%, paid with wages and shown separately on the payslip. Both calculations take hours per pay period as their input.

How long do we keep the records?

Six years, because minimum wage is almost always in play with hourly staff — regulation 59(8) of the NMW Regulations 2015. The two-year working time period is the shorter of the two and gets overtaken.

What is the penalty if the hours do not add up?

Since 7 April 2026 the regime is Part 5 of the Employment Rights Act 2025. Under section 107 the penalty is 200% of the underpayment for each worker, capped at £20,000 per worker and with a £100 floor. The arithmetic that produces it starts with hours.

Does someone on four hours a week still get a break?

The rest break under regulation 12 is triggered by daily working time over six hours, not by contract type. A four-hour shift does not trigger it; a nine-hour shift does, whatever the contract says.

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Questions? Write to time@irot.com. We answer on working days, usually by the next one.