Claiming your CIS refund
Most CIS subcontractors are owed money at the end of the year, because a flat 20% takes no account of your Personal Allowance or your expenses. The refund is not automatic. You claim it by filing a tax return.
Updated 10 September 2026 · Tax year 2026/27
Why the overpayment happens #
CIS is deliberately blunt. It takes a fixed percentage of your labour and sends it to HMRC. It does not know two things that matter enormously:
- Your first £12,570.00 of income is tax free
- Your tax is charged on profit, after expenses, not on turnover
A subcontractor with £38,000 of income, £6,000 of expenses and £6,400 deducted through CIS actually owes about £5,050 in Income Tax and Class 4 National Insurance. The difference comes back. Estimate yours.
What a CIS refund claim actually is #
There is no separate CIS refund claim form. The claim is your Self Assessment tax return. You declare your income and expenses, you enter the total CIS deducted during the year, and HMRC works out the difference. If more was deducted than you owed, the balance is repaid.
That is why nothing arrives automatically. No return, no claim, no refund, however much was taken from your payments.
What you need before you start #
- Every CIS payment and deduction statement for the tax year
- Your invoices, or your own record of income
- Receipts and records for expenses
- Your Unique Taxpayer Reference and Government Gateway login
- Details of any other income in the same year
The statements are the critical part, because they are the evidence for the deductions you are reclaiming. What a CIS statement must show.
The expenses people forget #
Understating expenses is the most common way subcontractors leave money behind. Every pound of genuine expense you miss costs you roughly 26p in overpaid tax and National Insurance at basic rate.
- Materials you paid for and were not separately reimbursed
- Tools, and replacing tools
- Van running costs, or mileage at the flat rate instead
- Protective clothing and safety equipment
- Public liability and tool insurance
- Phone, apportioned for work use
- Accountancy and bookkeeping fees
- CITB levy, trade body subscriptions, certification and card renewals
- Use of home for paperwork and quoting
The dates #
| Date | What happens |
|---|---|
| 5 April | Tax year ends |
| 6 April | You can file for the year just ended, and the earliest filers are paid first |
| 31 October | Deadline for a paper return |
| 31 January | Deadline for an online return, and for paying anything owed |
There is no reason to wait until January. If you are due a refund, filing in April means being paid months earlier, and HMRC is far less busy.
How long it takes #
HMRC generally pays within a few weeks of processing the return. It takes longer if the return is picked for checks, if your bank details are missing, or if the deductions you claimed do not match what contractors reported.
That last one is worth understanding. Contractors file monthly CIS returns telling HMRC what they deducted from whom. If your figure does not match theirs, the claim stalls. A contractor who never filed properly is the usual cause, and it is another reason to keep your statements.
Should you use a refund agent #
Plenty of firms advertise CIS refunds and take a percentage, often 20% to 30% of what you get back. On a £1,300 refund that is £260 to £400.
They are not doing anything you cannot do. A straightforward CIS return with one income source and ordinary expenses is a couple of hours' work. Where an accountant genuinely earns their fee is a complicated year: multiple income sources, a van bought on finance, a move to a limited company, or a dispute over missing statements.
If you do use someone, check whether the fee is a percentage or a flat rate, and be careful about signing anything that assigns the repayment to them rather than paying it to you directly.
If you owe instead #
It happens, usually when profits are high enough that the bill exceeds what CIS collected, or when a chunk of income came from work outside CIS. The balance is due by 31 January. If profits are large you may also be asked for payments on account towards the following year, which catches people out the first time.
Common questions #
How do I make a CIS refund claim?
Through your Self Assessment tax return. There is no separate CIS refund claim form. You declare your income and expenses, enter the total CIS deducted, and HMRC repays the difference.
How long does a CIS refund take?
Generally a few weeks after HMRC processes the return. It takes longer if the return is selected for checks, if bank details are missing, or if your deduction figures do not match what contractors reported.
Do I have to use a CIS refund agent?
No. Agents typically take 20% to 30% of the refund, which is £260 to £400 on a £1,300 repayment. A straightforward return with one income source is a couple of hours of work.