When calculating the national minimum wage (NMW) for on-call and sleep-in workers, do you count all hours in their shift, or just the time they are awake and carrying out duties?

The Supreme Court considered this question in relation to care workers undertaking 'sleep-in shifts' in Royal Mencap Society v Tomlinson-Blake.

How you calculate the NMW depends on whether work is classed as time, salaried, output or unmeasured work – the Supreme Court decision and this article relate to time and salaried work.

The facts

Mrs Tomlinson-Blake was a care worker providing support for vulnerable adults in their home. Her employer was obliged (via legislation and its contract with the local authority) to have someone on the premises throughout the night. She worked sleep-in shifts from 10pm to 7am. During her shifts she had to remain at the house, but:

  • had no specific tasks;
  • slept in a bedroom and was expected to get a good night's sleep (particularly as she might be expected to work a dayshift the following day); and
  • had to keep a 'listening ear' during the night in case support was needed and intervene if necessary (for example, if the individual was unwell or distressed). The need to intervene was 'real but infrequent' - she had been disturbed only about 6 times in 16 months.

Mr Shannon was an on-call night care assistant in a care home and was given free accommodation within the home. He had to be in the flat from 10pm – 7am but could sleep during this period and was rarely called upon for assistance.

Supreme Court decision

The Supreme Court found that only the hours both workers were 'awake for the purposes of working' should be counted for NMW purposes. So, time sleeping, or awake but not working, should not be counted.

Will this apply to all 'on-call' and 'sleep-in' shifts?

Not necessarily. Regardless of whether a shift is labelled 'on-call' or 'sleep-in', what matters is whether, in practice, a worker is 'working' throughout the shift, or just 'available'. This will depend on the facts, and there are likely to be many borderline cases. 

For sleep-in staff, the difference has been described as:

  • Working: staff are expected to work for most of a shift, albeit that there are short lulls in activity during which they can sleep.
  • Available: the 'essence of the arrangement' is that staff are expected to sleep for all or most of the period but may be woken if required to undertake specific activities.

The Supreme Court in Mencap noted a person can be 'working' even although their tasks are intermittent – just because someone can make a cup of tea, or even have a nap, between tasks, does not necessarily mean they are 'available' rather than 'working'.

Which hours count for the NMW calculation?

If a worker is 'working' throughout their shift, include all hours.

If they are not working, but are 'available' then include all hours they are required to be available at or near a place of work for the purposes of working unless one of the following applies:

  • They are at home. If they are at home and just need to be 'available', perhaps to respond to emergencies, you only need to include hours when they actually work; not the full duration of their on-call time (no matter whether they are awake or asleep).
  • They are sleeping, or permitted to sleep. You only need to include hours when the worker is 'awake for the purposes of working', even if they sleep at or near the workplace and you provide sleeping facilities.

Important – NMW is based on average hourly rate

To check whether a worker is receiving the NMW, you use their average hourly rate (i.e. total pay in a reference period divided by total hours worked in that period). So, even if you do need to include all hours worked on a shift in your NMW calculation, you may not need to pay the NMW rate for each of those hours individually. A worker's pay might otherwise by high enough that an hourly standby rate below the NMW does not, overall, reduce their average hourly rate below NMW rate levels.

The position for care workers in Scotland

Since October 2016, the Scottish Government has provided funding to enable adult social care workers to be paid the 'real living wage' for waking hours. During 2018/19, this was extended to all hours worked, including sleep-overs. Money is provided via the Scottish Government to local authorities to fund this for all commissioned contracts. This means that providers commissioned by local authorities to provide care should be paying staff the real living wage as a minimum for all hours worked, including sleep-overs. This covers adult social care workers providing direct care and support to adults in care homes, care at home, day care and housing support.

If you need advice on payments to your on-call or sleep-in workers, please get in touch, or Workbox subscribers can find more detail and examples at On-call and sleep-in workers: NMW.


Kathleen Morrison

Practice Development Lawyer

Emily Russell

Trainee solicitor