If you work in construction as a subcontractor, your contractor deducts 20% from every payment (30% if you're not registered) and sends it to HMRC. But those deductions ignore your personal allowance and your expenses — which is why most CIS workers overpay through the year and are owed money back. The refund isn't a bonus or a loophole. It's your own tax, returned.
Why the overpayment happens
- The 20% comes off the full invoice — before your £12,570 personal allowance is counted.
- Tools, travel, fuel, protective clothing, phone and insurance are deductible — the deduction ignores them all.
- The refund is claimed once a year, through your Self Assessment return after 5 April.
What a realistic refund looks like
It depends entirely on earnings and expenses, which is why we built a calculator: put in your CIS statements and expenses and see the range instantly on our CIS refunds page. Higher earners with real expenses routinely see four-figure refunds; anyone promising a fixed 'guaranteed' amount before seeing your records is selling something else.
What you need to claim
- CIS deduction statements from each contractor (or bank records to reconstruct them — we do this often).
- A note of your expenses: receipts, mileage, tool purchases.
- Your UTR — and if you've never registered, that's step one.
- Registration as a CIS subcontractor keeps you at 20% instead of 30% — worth fixing immediately if you're on the higher rate.
How fast it arrives
File early — refunds for returns filed in April and May are usually back within weeks. We prepare the return, maximise the legitimate expense claim, chase HMRC if it drags, and take nothing until you've seen the numbers.