CIS refund calculator 2026/27 with the working shown
A CIS refund is the tax your contractors deducted minus the tax actually due on your profit. On £28,000 of gross pay at 20% with £3,500 of expenses, £5,600 was deducted, income tax on the profit is £2,386, and the estimate is about £3,214. Class 4 National Insurance on the same profit is £716, so the real refund is nearer £2,500. The calculator below works to the same rules and labels itself an estimate for that reason.
The calculator
Three figures from your statements. Nothing is stored and no details are asked for.
Estimate your refund
Put in what you were paid and the estimate appears here.
An estimate, not a calculation. Income tax only at 2025/26 rates with a £12,570 personal allowance; it ignores National Insurance, student loans, other income and anything HMRC already owes or is owed. The return itself is prepared properly from your statements.
The working, on a £28,000 year
The same rules the calculator uses, written out. Rates are the 2025/26 figures on gov.uk, which also apply to 2026/27.
| Step | Amount | How |
|---|---|---|
| Gross pay on the statements | £28,000 | Before the contractor took anything off |
| Tax deducted at 20% | £5,600 | £28,000 × 20%. This is the advance payment HMRC already holds |
| Expenses | £3,500 | Van, fuel, tools, kit, phone, insurance |
| Profit | £24,500 | £28,000 less £3,500 |
| Personal allowance | £12,570 | Tax-free; the deduction at source ignored it |
| Taxable profit | £11,930 | £24,500 less £12,570 |
| Income tax due | £2,386 | £11,930 × 20% |
| Estimate on this page | £3,214 | £5,600 deducted less £2,386 due |
| Class 4 National Insurance | £716 | £11,930 × 6%. Charged on the return, not in the estimate |
| Refund the return would show | £2,498 | £3,214 less £716, before anything else on your return |
Why most subcontractors are owed money
The contractor deducts 20% of every payment. That deduction ignores two things the tax return allows: the £12,570 personal allowance and your expenses. On the example above, 20% of the gross is £5,600, but the tax and National Insurance actually due on the profit come to £3,102. The £2,498 gap is the refund. The higher your expenses and the lower your gross, the larger the gap; a subcontractor on £60,000 gross with small expenses can owe tax rather than be owed it, which the calculator also shows.
What the estimate leaves out
- Class 4 National Insurance at 6%, as above, and Class 2, which is treated as paid for most profits at this level.
- Any other income in the year: PAYE employment, rent, interest.
- Student loan repayments, which are collected through the return.
- Payments on account HMRC may ask for towards next year, which can be set against a refund.
- Anything HMRC already owes you or is owed from an earlier year.
A return prepared from your statements takes all of these into account. If you want that done by a named chartered accountant, the fee is £249, paid when you approve the return with the refund figure shown, or £149if the return shows no refund is due. If your year is as simple as the example, HMRC's own online return is free and will get you the same £2,498.
Common questions
Why is the real refund lower than the calculator says?
Because the calculator works out income tax only. The return also charges Class 4 National Insurance at 6% on profits between £12,570 and £50,270, and that comes out of the deductions before anything is refunded. On the £28,000 example it is £716. The calculator says so under the result; a return is prepared from your statements, not from this page.
Does it matter whether I was on 20% or 30%?
A great deal. At 30% the contractor took £8,400 from £28,000 instead of £5,600, so the refund is £2,800 bigger. The tax due is the same. If you were deducted at 30% because you never registered, register now; it changes every future payment.
What counts as an expense?
Costs of doing the work: van costs or a mileage rate, fuel, tools, protective clothing and boots, a work phone, public liability insurance, accountancy fees. Ordinary clothes, lunches and travel from home to a single regular site generally do not count. Every pound of allowable expense reduces the tax due by 20p at the basic rate, and so raises the refund by 20p.
See your own number
Three figures from your CIS statements give you an estimate on the page before you give a name. The fee is fixed and HMRC pays the refund to you.
Estimate my refundRelated
Sources
- GOV.UK: Income Tax rates and Personal Allowances: £12,570 allowance, 20% basic rate to £50,270.
https://www.gov.uk/income-tax-rates - GOV.UK: Self-employed National Insurance rates: Class 4 at 6% on profits between £12,570 and £50,270.
https://www.gov.uk/self-employed-national-insurance-rates - GOV.UK: What you must do as a CIS subcontractor: 20% deduction if registered, 30% if not.
https://www.gov.uk/what-you-must-do-as-a-cis-subcontractor - GOV.UK: Pay tax and claim back deductions: HMRC takes the deductions off the tax owed and refunds any balance.
https://www.gov.uk/what-you-must-do-as-a-cis-subcontractor/pay-tax-and-claim-back-deductions - Low Incomes Tax Reform Group: Construction industry scheme (CIS): worked example of setting CIS tax against Self Assessment.
https://www.litrg.org.uk/working/self-employment/construction-industry-scheme-cis