The 48-hour week and night work limits when software sets hours (UK)

Scheduling software can fill every open shift with whoever is available, and tracking software can measure every logged-in minute. Neither decides how much work is lawful. In Great Britain the Working Time Regulations 1998 cap average weekly hours and the length of night work, and require records that show the limits are kept. The Regulations apply to workers, not only employees. For daily and weekly rest and breaks, see UK rules on software-set rotas.

The short answer: a worker's working time, including overtime, must not exceed an average of 48 hours for each seven days, normally averaged over 17 weeks, unless the worker has agreed in writing to opt out (reg 4). A night worker's normal hours must not exceed an average of eight hours in each 24, and night workers must be offered free health assessments (regs 6 and 7). Employers must keep records adequate to show compliance for two years (reg 9).

What counts as working time

Working time means any period during which the worker is working, at the employer's disposal and carrying out their activity or duties; any period of relevant training; and any additional period treated as working time under a relevant agreement (reg 2(1)). Logged-in time on a system is evidence, but the legal test is the one in the definition, not what the software counts.

The 48-hour average week

Unless the employer has first obtained the worker's agreement in writing, the worker's working time, including overtime, in any applicable reference period must not exceed an average of 48 hours for each seven days (reg 4(1)). The employer must take all reasonable steps, in keeping with the need to protect health and safety, to ensure the limit is complied with (reg 4(2)).

The reference period is any period of 17 weeks in the course of the employment, or successive 17-week periods where a relevant agreement provides for that (reg 4(3)). For someone who has worked for the employer for less than 17 weeks, it is the time since they started (reg 4(4)). Days of annual leave, sick leave, and maternity, paternity, adoption or parental leave are excluded from the average and made up from the days worked after the reference period ends (reg 4(6) and (7)). A rota tool that only checks the current week, or treats leave days as zero hours, can therefore get the average wrong.

The opt-out

A written opt-out may be for a specified period or indefinite. The worker can end it by giving at least seven days' notice in writing, unless the agreement sets a different notice period, which cannot exceed three months (reg 5(2) and (3)). The employer must keep up-to-date records of the workers who have opted out (reg 4(2)).

A worker has the right not to be subjected to a detriment by the employer because they refused to forgo a right under the Regulations, or refused to enter into, vary or extend an agreement the Regulations provide for, such as an opt-out (Employment Rights Act 1996, s45A(1)). Software that gives fewer shifts or lower priority to people who have not opted out needs to be checked against that.

Night work

Unless a relevant agreement sets a different period, night time is 11 pm to 6 am. A night worker is someone who, as a normal course, works at least three hours of their daily working time during night time, which includes working such hours on the majority of days they work (reg 2(1)).

A night worker's normal hours of work must not exceed an average of eight hours for each 24 hours, averaged over 17 weeks unless a relevant agreement provides otherwise (reg 6(1) and (3)). Where the night work involves special hazards or heavy physical or mental strain, the worker must not work more than eight hours in any 24-hour period in which they do night work. Work counts as such if a collective or workforce agreement identifies it, or the employer's own health and safety risk assessment recognises it as a significant risk (reg 6(7) and (8)).

Before an adult worker is assigned to work that will make them a night worker, the employer must ensure they have the opportunity of a free health assessment, unless an earlier assessment is still valid, and must offer night workers free assessments at appropriate regular intervals (reg 7(1)). Where a registered medical practitioner advises that a worker's health problems are connected with night work, and suitable day work is possible, the employer must transfer them (reg 7(6)). Young workers have additional protections (reg 7(2)); see the rules for young workers.

Records

The employer must keep records adequate to show whether it has complied with the 48-hour and night work limits and the health assessment requirements, and keep them for two years from when they were made (reg 9(1)). The records may be kept in whatever manner and format the employer reasonably thinks fit, and the employer need not record each worker's daily hours if it can show compliance without doing so (reg 9(2) and (3)). Where time data already sits in a scheduling or tracking system, it should be possible to produce the 17-week averages from it.

Practical steps

• Employers: build the 48-hour average and the night work limits into the scheduling tool as hard limits, calculated over the correct reference period with leave days handled as the Regulations require. Keep opt-out agreements and the list of who has opted out up to date, and make sure no allocation rule penalises people who have not opted out. Arrange free health assessments before anyone becomes a night worker.
• Workers: keep your own record of hours, including overtime and training. You do not have to opt out of the 48-hour limit, and if you did, you can withdraw by giving written notice, normally seven days. If you work nights, ask for your health assessment. In a shop or betting office, you can also opt out of Sunday work. If you were placed by an agency, see agency workers' rights on working time after twelve weeks.

These Regulations extend to England, Wales and Scotland. This page is general information on the law in Great Britain as at 1 November 2026, not legal advice.