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CIS tax refund calculator 2026/27: estimate your subcontractor rebate

Contractors take 20% (or 30%) off your labour before you are paid, but that is only a guess at your tax. Once your materials, expenses and personal allowance are counted, many subcontractors have paid too much. Put in your year's figures to see roughly what should come back — or whether you still owe a little.

Checked for 2026/27 — uses the rates for 6 April 2026 to 5 April 2027, last reviewed 27 October 2026.

Your figures

Add up the gross figures on your CIS payment statements for 6 April 2026 to 5 April 2027, including any materials you charged for.

CIS is not taken from the materials part of a payment, and the cost is an allowable expense.

The total of the "deductions" boxes on your statements. Blank = we estimate it from your CIS status below.

Only used when the deductions box is blank.

Tools, protective clothing, van or mileage, phone, insurance, accountant fees and similar.

Wages taxed through PAYE in the same tax year. It pushes your CIS profit into a higher band.

Tick if you live in Scotland. Class 4 NI is the same across the UK.

Refund or bill

Estimated refund

£0

CIS deducted
£0.00
Taxable profit
£0.00
Income tax on your profit
£0.00
Class 4 National Insurance
£0.00
Your real tax bill
£0.00

Results update as you type. No sign-up, and nothing you enter leaves your device.

Worked example

Jordan is a registered plasterer in Leeds. In 2026/27 contractors paid £40,000 gross, of which £5,000 was for materials Jordan supplied. Other costs — van mileage, tools, insurance — came to £3,000. There was no other job.

Labour part of payments (£40,000 − £5,000)£35,000.00
CIS taken at 20% of labour£7,000.00
Profit: £40,000 − £5,000 − £3,000£32,000.00
Income tax: (£32,000 − £12,570) × 20%£3,886.00
Class 4 NI: £19,430 × 6%£1,165.80
Real tax bill£5,051.80
Estimated refund (£7,000 − £5,051.80)£1,948.20

The deductions were worked out on £35,000 of labour with no allowance for Jordan's costs or tax-free personal allowance, so roughly £1,950 has been overpaid. It comes back once the 2026/27 Self Assessment return is filed — from 6 April 2027 onwards.

How it works, in plain English

Under the Construction Industry Scheme, a contractor holds back part of each payment and sends it to HMRC on your behalf. It works like an advance payment of your income tax and National Insurance. At the end of the tax year your Self Assessment return compares what was held back with what you really owe.

What CIS is taken from

Deductions apply to the labour part of a payment only. Registered subcontractors lose 20%, unregistered ones 30%, and firms with gross payment status nothing at all. Money you are paid for materials you bought, and VAT, should not have CIS taken from it — check your monthly statements match.

What your real bill is based on

Your actual tax is worked out on profit: total gross pay minus materials and every other allowable cost. The first £12,570 of income is tax-free, the next £37,700 is taxed at 20% (Scotland uses its own bands), and Class 4 National Insurance adds 6% on profit between £12,570 and £50,270, then 2% above.

Refund or bill?

If the deductions add up to more than your real bill, HMRC repays the difference. Low earners, part-year workers and anyone with high costs usually get money back. If your profit is high, or you also had a job, the 20% may fall short and you will owe the balance by 31 January 2028.

Getting the money back

Sole-trader subcontractors claim through their Self Assessment return, which can be filed from 6 April 2027 for the 2026/27 year. Filing early means an earlier refund. Keep every payment and deduction statement: HMRC checks them against what contractors reported.

Frequently asked questions

How much CIS refund will I get?

It is the CIS deducted during the year minus your real income tax and Class 4 NI on your profit. The more expenses you have and the lower your profit, the bigger the refund. The calculator above does the sum for you.

When can I claim my CIS refund for 2026/27?

Once the tax year ends on 5 April 2027 you can file your Self Assessment return and the overpayment is repaid after HMRC processes it. You have until 31 January 2028 to file online, but there is no reason to wait if you are due money back.

Is CIS deducted from materials?

No. Contractors should only deduct CIS from the labour element of your invoice. If materials are shown separately, they are paid in full — and the cost of buying them still counts as a business expense on your return.

Why do I owe tax when CIS was already taken?

A flat 20% does not cover Class 4 NI or the 40% band. If your profit is well above about £30,000, or you also had a PAYE job, the deductions can fall short of your real bill and the difference is due by 31 January.

What expenses can a CIS subcontractor claim?

Common ones are tools and equipment, work clothing and protective gear, van costs or 45p a mile on a car, phone, public liability insurance, training and accountancy fees. Travel from home to a temporary site usually counts too. Ordinary clothes and food do not.

I lost my CIS statements. What can I do?

Ask each contractor for copies — they must give you a monthly statement. You can also see deductions reported against your UTR in your HMRC online account before filing. Use the statements, not bank transfers, as the deducted total.

Estimates only, not tax advice. These figures are a guide based on the information you enter and the 2026/27 rules. Your own position can differ — check GOV.UK or an accountant before relying on them.