Unpaid overtime in the UK : calculate what you are owed
No automatic statutory overtime premium in the UK: contractual rates, National Minimum Wage risks when extra hours are unpaid, and the separate 48-hour average working time limit.
You stayed late. You covered a Saturday. The rota grew, the inbox kept pinging after clock-off, and the next payslip still looks like a standard week.
In the UK there is a widespread myth that overtime must always be paid at time and a half. That is not what the statute says. Acas is blunt: there is no automatic legal right to overtime pay. What you can claim depends on your contract, on whether unpaid hours pull you below National Minimum Wage, and on separate working time limits under the Working Time Regulations.
In short
- No automatic statutory overtime premium. Higher rates (time and a half, double time, TOIL) come from the contract, a handbook term you were given, or a clear workplace agreement, not from a general overtime statute.
- Employers must state in the written statement of employment particulars what counts as overtime and what rate applies.
- Extra hours that are unpaid (or paid too low) can still breach National Minimum Wage once you average pay over the hours that count.
- The 48-hour average weekly limit is a working time rule. It is separate from whether overtime is paid.
- Most pay claims still face a 3 months minus 1 day tribunal limit (September 2026); from 1 October 2026 most claims become 6 months minus 1 day if the clock starts on or after that date.
What Acas says about overtime pay
Acas’s overtime guidance explains that some employers choose to pay for hours beyond the contract. That is usually called overtime pay. Although some employers offer it, there is no automatic legal right to it.
What employers must put in the written statement of employment particulars includes:
- what hours are classed as overtime
- what the rate of pay is for overtime
Some employers offer a higher rate than normal hours. Others offer time off in lieu (TOIL) instead of cash. Both are contractual or policy choices, not a universal legal premium.
If you are part-time, Acas notes that by law you must not be treated less favourably than a comparable full-time worker. On overtime, part-time staff are not entitled to overtime pay until they have worked more than the normal hours of full-time staff, unless your organisation’s contract or policy says something more generous. Always check the written terms.
Contract first: find the overtime clause
Before you argue about “overtime law”, open the paperwork:
- Written statement / contract - normal hours, overtime definition, rate or TOIL.
- Staff handbook - only if it forms part of your terms or was clearly issued as binding.
- Payslips - do overtime hours appear when pay varies with time worked? (See ERA section 8 and GOV.UK payslip rules.)
- Messages and rotas - proof you were asked or expected to work the extra time.
If the contract says overtime is paid at £18 an hour, unpaid overtime is a wages problem under the Employment Rights Act framework Acas describes for unpaid pay. If the contract is silent on a premium but you still worked extra hours, you may still have a claim that those hours should have been paid at least at your normal rate, or that average pay fell below National Minimum Wage. Do not invent a statutory “time and a half” if the contract never promised it.
National Minimum Wage: unpaid hours can still break the floor
Acas states the NMW link clearly: if someone works more hours than the contract says, the employer must make sure the hourly rate does not fall below National Minimum Wage.
GOV.UK’s calculating the minimum wage guidance explains that NMW is an hourly test even if you are paid a salary or a day rate. You work out pay that counts for NMW, divide by hours that count for that type of work in the pay reference period, and check the result against the legal rate.
From April 2026, workers aged 21 and over are entitled to £12.71 an hour (GOV.UK NMW rates). Younger rates differ; always check the live table.
For time work (paid by the hour), hours at the workplace working generally count, and so can time when you must be available at work. Ordinary rest breaks usually do not count as NMW working time for time workers. Commuting between home and work usually does not count. Training required by the employer often does. The detailed rules sit in the GOV.UK manual; the practical message is simple: extra unpaid work stretches the hour count and can drag the average under £12.71 even if your “headline” rate looked fine on the offer letter.
For salaried hours work, GOV.UK explains that once you exceed basic annual hours, excess unpaid hours must still be brought into the NMW check for later pay reference periods. “You’re salaried so overtime doesn’t exist” is not a complete answer if the unpaid extras push you below the legal floor.
Working time: the 48-hour average is a separate rule
GOV.UK maximum weekly working hours sets out another limit: you cannot work more than 48 hours a week on average, normally averaged over 17 weeks, unless you opt out in writing. Under-18s have stricter daily and weekly caps.
This rule is about how long you can be required to work on average. It is not an automatic overtime pay guarantee. You can be inside the 48-hour average and still be owed contractual overtime. You can also have opted out of the 48-hour limit and still be protected by National Minimum Wage on every hour that counts.
Do not mix the conversations in one vague complaint. Say separately:
- “My contract pays overtime at X and these hours were not paid.”
- “Including unpaid hours, my average pay fell below National Minimum Wage.”
- “My average hours over the reference period exceed 48 without a valid opt-out” (if that is true).
Holiday pay and regular overtime
Acas notes that holiday pay must include overtime payments if you have regularly received overtime pay during the previous year. Relevant overtime must be included in at least 4 weeks of holiday pay for most employees, and in 5.6 weeks for irregular hours and part-year workers. Employers may include overtime in the full 5.6 weeks for everyone, but they do not have to for the extra 1.6 weeks in the standard case.
So unpaid overtime can hurt you twice: you lose the cash in the week you worked it, and your holiday pay average may be wrong later if overtime should have been paid and counted.
What to do if overtime is unpaid
- Calculate hours beyond normal, contractual rate or TOIL terms, and an NMW average check.
- Raise it in writing with manager or payroll. Attach rota evidence and the payslip.
- Grievance if informal contact fails. Remember: grievance does not stop the tribunal clock.
- Acas Early Conciliation before most employment tribunal claims. Notify within the time limit so the clock can pause.
- Tribunal or HMRC for NMW: Acas explains workers can complain about minimum wage underpayment; for contractual wages, the tribunal wages route is common. Get advice if you are choosing between routes for the same shortfall.
Dual time-limit regime: most pay claims remain 3 months minus 1 day as at September 2026. From 1 October 2026, most claims become 6 months minus 1 day if the time limit starts on or after that date (Acas).
Common traps
- Assuming time and a half is “the law”. It is usually the contract talking, not a general statute.
- Ignoring NMW because the hourly rate on paper looks legal. Extra unpaid hours change the average.
- Confusing TOIL that never arrives with “flexibility”. If the deal was time off instead of pay, diary when the lieu time should have been given.
- Part-time overtime expectations. Check when overtime rates kick in compared with full-time normal hours.
- Opt-out myths. Signing away the 48-hour average does not sign away NMW or contractual overtime.
- Waiting for a busy season to end. The limitation clock runs from when you were not paid correctly.
Soft next step with Paye Mes Heures
Extra hours are easier to argue when they are logged against each payday. Paye Mes Heures can help you estimate unpaid overtime and NMW-style shortfalls so your email to HR or Acas starts with numbers, not frustration. It prepares a dossier; it does not replace Acas, HMRC, legal advice, or a tribunal.
Unpaid overtime in the UK is rarely about a mythical statutory premium. It is about the contract you were given, the legal wage floor, and the working time limits that sit beside pay, not instead of it.