Can I claim back CIS deductions from previous years?

Usually yes, for up to 4 years after each tax year ends. As at 16 October 2026, the oldest year you can normally still claim is 2022-23, and that return must reach HMRC by 5 April 2027.

Construction Industry Scheme (CIS) deductions are advance payments towards your tax. A sole trader gets any excess back by filing a Self Assessment tax return for the year. If you never filed one, the money stays with HMRC. Section 34A of the Taxes Management Act 1970 sets the general limit: a return can be made up to 4 years after the end of the tax year it covers. HMRC's manual says it does not process returns that arrive after that.

Deadlines by tax year

The normal deadline is when the return is due. Filing after it can bring penalties. The last column is the latest date HMRC can accept the return at all.

Two exceptions to the 4-year rule

A notice to file. If HMRC sent you a notice to file a return within the 4 years, section 34A gives you 3 months from the date of that notice, even if this runs past the 4 years.

A determination. If you did not file when asked, HMRC may have issued a determination, which is its own estimate of your tax. HMRC's manual says a determination can only be replaced by your own return within 3 years of the filing date, or within 12 months of the determination if that is later. For 2022-23, whose filing date was 31 January 2024, that 3-year point is 31 January 2027. If you have a determination for 2022-23, aim to file before then rather than relying on 5 April 2027.

What this means for you

If you worked under CIS and never filed, you may have several years of over-deducted tax waiting for you. Each year is a separate return with its own deadline, and the oldest one is always the one closest to being lost. In October 2026, that is 2022-23.

If you did file but left something out, such as CIS deductions or business costs, GOV.UK says you can correct a return within 12 months of the Self Assessment deadline. For 2024-25, that usually means by 31 January 2027. After that, you write to HMRC to claim overpayment relief, which is also limited to 4 years after the end of the tax year. Your letter must say it is a claim for overpayment relief, which year, why you think you overpaid, how much, and whether you have appealed before.

Late filing penalties may apply where HMRC had asked you to file: £100 straight away, then more after 3, 6 and 12 months. HMRC's manual also says a repayment only covers deductions above your tax for that year and any tax still unpaid on earlier years' profits.

Steps to claim earlier years

1. List every tax year you worked under CIS and whether you filed a return for it.
2. Check your letters for notices to file and determinations from HMRC. They change the deadline.
3. Start with the oldest year still in time. In October 2026 that is 2022-23, with a deadline of 5 April 2027.
4. Gather the payment and deduction statements for each year, and ask contractors for duplicates of any that are missing.
5. If a contractor has gone out of business, write to HMRC at PT Operations, BX9 1BX, with your UTR, their details and the dates you were paid.
6. Total your gross pay, deductions and business costs for each year, and keep the receipts.
7. File each return, using the forms for that year, with your bank details so HMRC can repay you.
8. For a return you already filed, amend it if you are within 12 months of its deadline, or write to HMRC to claim overpayment relief.

Old years are where outside help most often pays for itself, especially with penalties or determinations involved. Over-deducted CIS is claimed back through your tax return. The sooner you file, the sooner HMRC can repay you.

Use the free MTD check to see whether Making Tax Digital applies to you from April 2027, and visit the trades section for more on CIS.