SiteIt's the first week of June. Two of your fitters are on holiday and a third is off with a bad back. You've got an agency engineer on nights covering the gap. A good one, who knows the packers.
Then the bad back turns into an operation. Holiday cover rolls into sickness cover. Nobody books it as a long job. It just gets extended, a week at a time.
By September that engineer has been on your site for three months. Somewhere in week 13 the rules changed. Nobody on your side noticed.
That's the problem. The 12-week clock runs whether you watch it or not.
What they get from the first shift
Two rights start on day one. Under the Agency Workers Regulations 2010, an agency worker must be treated no less favourably than a comparable worker on "collective facilities and amenities" (regulation 12). The regulation names canteens, child care and transport. The government's guidance for hirers adds car parking, toilets and showers, and food and drinks machines (DBT guidance). Worse treatment is only allowed if you can justify it on objective grounds.
They also have the right to hear about your vacancies (regulation 13). Advertise a shift fitter job internally and the agency engineer gets to see it. A notice in a suitable place on site is enough.
These two are yours, alongside your health and safety duties to agency workers. The hirer is liable for any breach of them, not the agency (regulation 14).
How the clock counts
To qualify for equal treatment, the worker must work "in the same role with the same hirer for 12 continuous calendar weeks*" (regulation 7). Any week they work, even part of it, counts as a week. One shift is enough. The guidance says a calendar week is any seven days starting with the first day of the assignment. So if your engineer works every week with no gaps, the 12 weeks are done after 84 days. Equal treatment starts on day 85*.
Breaks make it messy. The guidance pictures a clock that can pause, reset to zero or keep ticking.
It pauses, then carries on from where it stopped, for:
- a break for any reason of six calendar weeks* or less, if they come back to the same role
- sickness or injury, for up to 28 weeks*
- leave they're entitled to, including annual leave
- jury service, for up to 28 weeks*
- a planned shutdown, like the Christmas shut or the summer shut
- a strike or lock-out at your site
It keeps ticking through pregnancy and maternity-related absence, and through maternity, adoption and paternity leave.
It goes back to zero after a break of more than six weeks* that isn't on that list, or a move to a role that's "substantively different". A move to a new hirer resets it too. The guidance treats separate companies in the same group as separate hirers.
Moving lines doesn't restart the clock
For the clock to restart, the work or duties that make up the whole or main part of the new role must be substantively different. The agency also has to tell the worker in writing what the new role involves (regulation 7).
The guidance is blunt about what doesn't count. A new line manager doesn't. A new pay rate on its own doesn't. In its words, "There has to be a genuine and real difference to the role." The factors include different skills, extra training or a new qualification, different equipment, different hours and a different location. Its example: production line to packing is unlikely to be enough.
So moving your agency fitter from Line 2 to Line 4 restarts nothing. Moving between your own sites usually doesn't either. If you move someone off mechanical breakdowns and onto writing PLC code, that might count.
What changes on day 85
From then on, the worker is entitled to the same basic working and employment conditions they'd have got if you'd hired them directly (regulation 5). Regulation 6 lists what that covers: pay, the duration of working time, night work, rest periods, rest breaks and annual leave.
For maintenance cover, pay is where it bites. The guidance says pay includes basic pay, overtime (once they meet the same qualifying hours as your staff), shift and unsocial hours allowances, and risk payments. If your own fitters get a nights premium, the agency fitter on the same nights should get it too. Holiday pay counts, and so does extra annual leave if your own team gets more than the legal minimum.
Some things are left out. Regulation 6 excludes occupational sick pay, pensions, redundancy pay, pay for maternity, paternity and adoption leave, expenses, share schemes, and bonuses that reward loyalty or long service.
Don't rotate people to dodge it
You're allowed to end an assignment at 11 weeks. The guidance says so. What you can't do is build a pattern of assignments to stop someone reaching 12 weeks. That's the anti-avoidance rule in regulation 9. A tribunal looks at how long the assignments were, how many there were, the role changes and the breaks between them. If the most likely explanation is that you meant to block equal treatment, the worker is treated as having qualified anyway. On top of the normal compensation, the tribunal can add up to £5,000* (regulation 18).
Here's our view. Swapping a good engineer out every 11 weeks is a poor plan even when it's legal. You lose someone who knows your kit, and pay the next one to learn it, often mid-breakdown. If the cover is going to be long, plan it as long cover. Budget for equal pay from day 85 and keep the person who already knows where the isolators are.
Wrong numbers land on you
Both you and the agency can be liable for an equal treatment breach, each to the extent it's responsible (regulation 14). The agency has a defence if it took reasonable steps to get the right information from you and acted on it. Then the liability falls on you. The guidance says that if a hirer gave no information, or wrong information, the liability "could be the sole responsibility of the hirer."
So give the agency your real figures for the fitters doing the same work. Basic rate, shift premiums, overtime rules, holiday terms. Tell them again after every pay award.
If the worker thinks they've been short-changed, they can ask the agency for a written statement. If the agency hasn't sent one within 30 days*, they can ask you, and you have 28 days* to reply (regulation 16). If a claim succeeds, the award is normally at least two weeks' pay* (regulation 18).
What the agency owes you up front
The Conduct of Employment Agencies and Employment Businesses Regulations 2003 run the other way. Before supplying anyone, the agency must get from you the start date and likely duration, the type of work, the hours and location, the known health and safety risks, and the qualifications you need (regulation 18). It must confirm the person's identity, and that they have the experience, training, qualifications and authorisations you asked for (regulation 19). When it proposes someone, it must pass that on to you. If that wasn't in writing, it must confirm it on paper or electronically within three business days* (regulation 21).
Use that. The duration you give the agency on day one is the start of the paper trail on how long this cover really runs.
All of this comes from the regulations and the government's guidance. It isn't legal advice, so take advice for your own case.
What to do on Monday
- List every agency engineer on site with their start date and role. Count the weeks yourself, pauses included.
- Send each agency your current rates, shift premiums, overtime rules and holiday terms for the fitters doing the same work.
- For any cover past eight weeks, decide now. Long cover with equal pay from day 85, or a planned end date you can explain.
- Check your vacancies go up where agency staff can see them.
* The 12-week qualifying period, the six-week and 28-week break rules, the 30-day and 28-day statement deadlines, the two weeks' pay minimum award, the £5,000 anti-avoidance award and the three business day confirmation are correct as of 27 September 2026. Check the Agency Workers Regulations 2010, the Conduct Regulations 2003 and GOV.UK for the latest. Day 85 assumes the engineer works in every calendar week with no breaks; any pause pushes it back.