Written by the TaxTune Editorial Team · Reviewed by our qualified accountants · Updated for 2026
The quick answer To claim a CIS refund as a sole trader, you file a Self Assessment return showing your income, the CIS already deducted, and your allowable expenses. Because CIS is taken before expenses, the deductions often exceed your actual tax, and HMRC refunds the difference, usually within a few weeks of filing.

How to claim, step by step

  1. Gather your deduction statements. Collect a statement from every contractor showing the CIS taken from your pay across the year.
  2. Total your income and expenses. Add up your gross income and every allowable cost, from tools and materials to travel and insurance.
  3. File your Self Assessment return. Enter your income, expenses and the total CIS deducted. HMRC compares the tax due to the tax already taken.
  4. Claim the refund. Where CIS exceeds your actual tax, HMRC refunds the difference to your bank account.
  5. Keep records. Hold onto statements and receipts for at least 5 years in case HMRC checks.

Getting the full amount

The size of your refund depends on claiming every allowable expense. Missed tools, mileage or protective clothing all mean a smaller refund. This is where many subcontractors leave money behind by rushing the return.

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Frequently asked questions

How do I claim a CIS refund?

File a Self Assessment return showing your income, allowable expenses and the CIS deducted. Where the CIS taken exceeds your actual tax, HMRC refunds the difference.

How long does a CIS refund take?

Once the return is filed and processed, refunds are often paid within a few weeks, though timing varies with HMRC checks and the time of year.

Why am I owed a CIS refund?

Because CIS is deducted from your pay before your expenses and personal allowance are taken into account, so the tax taken often exceeds what you actually owe.

What records do I need for a CIS claim?

Every CIS deduction statement from your contractors, plus receipts for your expenses. Keep them for at least 5 years in case HMRC reviews the claim.

Can an accountant increase my refund?

Often yes, by claiming every allowable expense you are entitled to. Underclaiming expenses is the most common reason subcontractors receive a smaller refund than they should.