The General Principle
Under the Working Time Regulations 1998 (WTR 1998) and principles established under the EU Working Time Directive (2003/88/EC), on-call duty (standby) is generally not considered statutory working time so long as the employee is merely required to be contactable and remains free to choose their location. Unlike on-site standby duty (where the worker is required to remain at the employer's premises), ordinary on-call time can run concurrently with statutory daily rest periods.
The Limitation Established by the ECJ
The European Court of Justice (ECJ) and UK employment tribunals have refined this principle: the decisive factor is whether the constraints imposed on the worker significantly restrict their ability to pursue personal and leisure activities.
Factors such as an extremely short response or arrival time (e.g. required on-site within minutes), a high frequency of call-outs, or strict operational requirements (such as remaining in uniform or near specialized equipment) can mean the entire standby period must be classified as statutory working time. Determining whether standby constitutes working time requires an objective evaluation of all the circumstances of the specific case.
Effect on Rest Periods
If an employee is called out to work during an on-call period, the active assignment interrupts the statutory daily rest period (the mandatory 11 consecutive hours of uninterrupted rest required under Regulation 10 of the Working Time Regulations 1998).
Under UK law, if a rest period is interrupted, the worker is entitled to an equivalent period of compensatory rest before commencing their next regular shift. A brief nocturnal call-out—even lasting only 20 minutes—can prevent the employee from completing their 11 consecutive hours of rest, making their scheduled start time the following morning legally problematic without compensatory rest. Implementing an automated time tracking system ensures that call-outs are recorded accurately and rest period compliance is maintained.
Remuneration and National Minimum Wage
How on-call time is compensated depends on the employment contract and National Minimum Wage (NMW) legislation:
- Contractual Pay: Employers frequently pay a standby allowance or flat-rate on-call retainer for being available, with actual call-out hours paid at the standard hourly rate or enhanced overtime/night rates.
- National Minimum Wage Compliance: Under the National Minimum Wage Regulations 2015, if a worker is merely on standby at home and free to engage in leisure activities, hours spent waiting do not count as time work for NMW purposes; only actual call-out work must meet or exceed NMW rates. However, if on-call constraints legally reclassify the entire standby period as working time, total pay over the pay reference period must ensure average hourly earnings satisfy the National Minimum Wage or National Living Wage.
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