How do I claim a CIS refund as a self-employed subcontractor?

You claim over-deducted CIS back through your Self Assessment tax return once the tax year ends on 5 April. There is no refund during the year while you are trading. For 2026-27, you can file from 6 April 2027.

Under the Construction Industry Scheme (CIS), every deduction your contractor takes is an advance payment towards your tax and National Insurance. Contractors take 20% of your labour if you are registered, but your actual bill depends on your profit after costs and your personal allowance. Many subcontractors end up paying more through CIS than they owe. Over-deducted CIS is claimed back through your tax return. The sooner after 5 April you file, the sooner HMRC can repay you.

How the refund works: a worked example

You invoice £40,000 of labour in the 2026-27 tax year and contractors deduct 20%. Your business costs are £8,000. You live outside Scotland, have no other income and get the full personal allowance.

These are 2026-27 rates. Class 2 National Insurance is treated as paid because the profit is above £7,105, so it adds nothing. This is an example only. Your own figures will differ.

What this means for you

Your CIS deductions are not lost money. They sit with HMRC against your name until you file. HMRC cannot repay you before then, so filing in April 2027 rather than January 2028 puts your claim in up to nine months earlier. The deadline for the 2026-27 tax return is 31 January 2028, but nothing stops you filing as soon as the year ends.

The claim is part of the tax return itself. There is no separate CIS refund form for a sole trader who is still trading. Be wary of anyone who promises a refund within the year or by a set date.

Steps to claim your CIS refund

1. Collect every monthly payment and deduction statement for the tax year, 6 April to 5 April. A contractor who takes a deduction must give you one within 14 days of the end of that tax month.
2. If any are missing, ask the contractor for a copy. If you cannot get one, for example because the contractor has gone out of business, write to HMRC with your details, the contractor's details and the dates you were paid.
3. Add up your total pay before deductions and the total deducted. Check each statement against your bank account.
4. Total your business costs for the year, such as materials you paid for, van and travel costs and phone bills, and keep the receipts.
5. Complete your tax return. Put your gross pay in as turnover and the total deductions as CIS deductions. On the 2025-26 paper forms that is box 38 of SA103S or box 81 of SA103F.
6. Give your UK bank account details on the return. HMRC usually pays the refund to that account.
7. File online soon after 5 April. If HMRC asks for evidence of your deductions, send it by the deadline it gives you.

Under Making Tax Digital

Making Tax Digital for Income Tax (MTD) changes how you claim, but not when. Once you are in MTD, GOV.UK says HMRC adds your CIS subcontractor deductions to your tax return for you. You must check them before you submit. GOV.UK also says you cannot claim the refund in an MTD tax return. You request it through your HMRC online services account instead, or your agent requests it for you.

If you start MTD on 6 April 2027, your 2026-27 tax return is still an ordinary Self Assessment return. Your first MTD tax return covers 2027-28 and is due by 31 January 2029. Quarterly updates are reports of your income and costs, not payments, and they do not trigger a refund.

If something looks wrong

• Wrong deduction rate. If you are registered but a contractor took 30%, they may not have verified you. GOV.UK says to speak to your contractor if you think the figures are incorrect. In October 2026 HMRC is writing to contractors whose returns show errors such as wrong deduction rates.
• You stop trading. GOV.UK says you may be able to claim back that year's deductions using form CIS40.

Use the free MTD check to see when MTD starts for you, and visit the trades section for more on CIS and the building trades.