Getting a CIS refund through your Self Assessment return, step by step
If contractors took 20% or 30% off your labour all year, you've probably paid more tax than you owe. As a sole trader, you get it back through your Self Assessment return. Here's the process for 2025/26, with a worked example.
Checked against GOV.UK on 23 October 2026. General information for sole traders in England, Wales and Northern Ireland, not tax advice. Scottish Income Tax rates are different.
Why many subbies are owed money
CIS deductions count as advance payments towards your tax and National Insurance. They're taken from your gross labour, but your tax is worked out on profit after expenses and the Personal Allowance, so the deductions often add up to more than the bill.
Worked example for 2025/26
| Labour invoiced | £36,000.00 |
| CIS deducted at 20% | £7,200.00 |
| Allowable expenses | £6,000.00 |
| Profit | £30,000.00 |
| Income Tax (£17,430 × 20%) | £3,486.00 |
| Class 4 NI (£17,430 × 6%) | £1,045.80 |
| Total bill | £4,531.80 |
| Refund due (£7,200 − £4,531.80) | £2,668.20 |
CIS covered more than 80% of the bill, so there are no payments on account to make either.
Step by step
- Collect every monthly CIS statement for the tax months from 6 April 2025 to 5 April 2026, and add up the deductions. Ask contractors for any that are missing.
- Check them against your invoices. Mismatches are a common reason HMRC queries a claim.
- Add up your income and expenses. Enter gross income before CIS, not what reached your bank.
- Enter the total CIS deductions in the self-employment section of the return. HMRC sets them against your bill.
- File as early as you can. You can file from 6 April 2026, and earlier filing means an earlier repayment.
Tips
- Only claim deductions shown on statements. HMRC checks what contractors reported.
- If 30% was taken because you weren't registered, register now so future deductions are 20%. See registering as a CIS subcontractor.
- A late return still gets the £100 penalty, even if you're owed money.
For a quick estimate, use the CIS refund calculator, or the January tax bill calculator for the full January picture. For background, see claiming back CIS deductions.
This guide is part of our Self Assessment guides for the self-employed.
Free: The UK Contractor's Cheat Sheet 2026/27
CIS rates, overtime maths, tax dates, mileage, VAT and late payment, on 2 pages. Keep it on your phone or print it for the van.
Frequently asked questions
How do I claim back CIS as a sole trader?
Through your Self Assessment return, by entering the total CIS deducted. HMRC sets it against your bill and repays any extra.
Can I claim a CIS refund before January?
Yes. You can file your 2025/26 return from 6 April 2026.
What if a contractor's statement is missing?
Ask the contractor. They must give you a statement for each month they made a deduction.
Is it the same for a limited company?
No. Limited companies reclaim CIS through their payroll submissions, not Self Assessment.
Sources
- What you must do as a CIS subcontractor – GOV.UK
- Understand your Self Assessment tax bill: payments on account – GOV.UK
- Income Tax rates: previous tax years – GOV.UK
- Self-employed National Insurance rates – GOV.UK
This guide is general information, not legal, tax or financial advice. Rules and rates change, so check the linked GOV.UK pages for the current position.