The anatomy of a £360 day
Take a site manager on a typical agency arrangement. The agency charges your business £360 a day. The manager is on a day rate of £300. The £60 in between is the agency margin, and it is charged on every single day the manager works for you, from the first day to the last.
There is nothing underhand about the number itself. The agency found the manager, vetted them, runs their payroll and carries a share of the employment admin. That is real work, and real work costs money. The problem is not that the margin exists. The problem is that it almost never appears on the invoice as a separate line, so most contractors never get to ask the only question that matters: what am I still paying for this week that I was not already paying for last week?
The year maths
Margin looks small by the day and enormous by the year. Five days a week for 48 weeks is 240 working days. At £60 a day, that is £14,400 a year in margin on one site manager. Not the manager's pay. Not tax. A fee for the introduction to somebody who, by month two, you already know, trust and manage yourself.
Run the same sum for every agency worker on your books and it becomes clear why the margin line deserves more attention than it usually gets. It is often the largest cost in the business that nobody has ever itemised.
VAT: the cashflow cost hiding in plain sight
Agency invoices carry VAT at 20 percent on the full charge, labour and margin together. On our site manager, £360 a day across 240 days is £86,400 of invoices, which means £17,280 of VAT paid out over the year. If you are VAT registered you get it back, but on the quarterly cycle, weeks or months after the money left your account.
That £17,280 is not a cost in the accounting sense. It is worse in one specific way: it is a rolling, interest-free loan you make with your own working capital, renewed every quarter, at exactly the moment most contractors are stretching to cover wages and materials. Engage the same person directly and there is no agency invoice sitting in the middle, so there is no agency VAT to front on that labour. How VAT falls in any direct arrangement depends on the worker's registration and the construction reverse charge rules, so check your own position with your accountant.
When an agency is worth every penny
Here is the part most platforms skip. Agencies solve real problems, and there are weeks when £60 a day is a bargain:
- Genuine emergency cover. Somebody drops out on Sunday night and you need a qualified body through the gate at 7.30 on Monday. That speed has value.
- One-off trades you will never book again. If you need a specialist for three days once a year, the margin is a fair price for the matchmaking.
- Unfamiliar patches. Starting a job two hundred miles from home, where you know nobody, an agency's local book is worth paying for.
- No back office. If nobody in your business can run verification, contracts and payroll, the agency is doing work you would otherwise do badly.
If your agency spend lives in that list, this guide has no argument with it. The argument starts when the spend stops living there.
The rebooking trap
Agency margin is easiest to justify on the first booking and hardest to justify on the fortieth. Once the manager has proven themselves, knows your sites and wants to keep working with you, the matchmaking is finished. The vetting is finished. What remains is a payroll service, priced at £60 a day, every day, indefinitely.
This is the quiet economics of labour supply: the fee is earned in week one and collected forever. An introduction fee became a standing toll, and because it is buried inside a single day rate, it never comes up for review the way a software subscription or an insurance renewal would.
The worked example, totalled
Put the year together for that one site manager:
- Agency margin: £14,400. £60 a day for 240 days.
- VAT fronted: £17,280, cycling through your working capital all year.
That is £31,680 either leaving the business or locked up in the VAT cycle, on top of the £300 a day the manager actually earns.
Now the alternative. Hire the same manager through the UrProject marketplace and the fee is £50 a week while they are on a live job, which is £2,400 across the same 48 weeks. The manager still gets their £300 a day, agreed and locked before they start. At the end of the year the business has kept £29,280 that the agency route would have consumed or tied up.
Run your own numbers
Every team is different. Rates, roles, weeks worked and how much of your labour is repeat business all move the answer, which is why a single headline figure should never be the end of the conversation. The agency margin calculator takes your day rates, your team size and your working weeks and shows the split the invoice hides. It takes about two minutes, and the maths follows the same method as the Specialist Contractor's Labour Manual, so you can check every step of it.
The margin is not a scandal. It is a price. The point of this guide is simply that you should get to see the price before you keep paying it.