The short answer: the CIS deductions on your monthly statements count as tax already paid. On your Self Assessment return HMRC works out the real Income Tax and Class 4 National Insurance on your profit (pay minus expenses, minus your £12,570 Personal Allowance for tax), takes off what contractors deducted, and refunds the difference. A subcontractor paid £32,000 with £4,500 of expenses gets about £2,500 back (worked example). You can claim for 2025/26 now: the deadline is 31 January 2027, and filing early gets the money sooner.
Jump to: Calculator · How the refund works · Worked example · Expenses you can claim · How to claim it · Missing statements · Traps · FAQ
CIS tax refund calculator
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Partners: enter your share of the partnership's profit as "other self-employed income" and your own CIS deductions. Limited companies claim CIS back differently (through the company's payroll), so this calculator isn't for them.
How a CIS refund works
Under the Construction Industry Scheme, a contractor takes 20% off the labour on each payment to you (30% if you're not registered or they can't verify you; nothing if you have gross payment status) and sends it to HMRC. gov.uk calls these deductions "advance payments towards your tax and National Insurance bill".
The trouble is that 20% is taken from your gross labour, with no allowance for:
- your Personal Allowance: the first £12,570 of income is tax-free (both 2025/26 and 2026/27);
- your expenses: tools, van, fuel, phone, materials you bought and the rest;
- the fact that Class 4 National Insurance is only 6% (on profit between £12,570 and £50,270, 2% above).
So most subcontractors overpay through the year, and the return is how you get it back. If your profit is high (roughly above £45,000 with no other income) the deductions may not cover the bill, and you'll owe the rest by 31 January instead.
| Rates used (2025/26 and 2026/27) | England, Wales, NI | Scotland |
|---|---|---|
| Personal Allowance | £12,570 (reduced by £1 for every £2 of income over £100,000) | |
| Income Tax on income above it | 20% to £50,270, 40% to £125,140, 45% above | 19% / 20% / 21% / 42% / 45% / 48% (bands: gov.uk) |
| Class 4 National Insurance on profit | 6% from £12,570 to £50,270, 2% above | |
| Class 2 National Insurance | None to pay. Profits under £6,845 (2025/26) or £7,105 (2026/27): optional, £3.50 or £3.65 a week, to protect your State Pension | |
Worked example: Jay, a plasterer
Jay subbed for three builders in 2025/26. Her statements show £32,000 gross, all labour, and £6,400 deducted at 20%. Her expenses come to £4,500 (van running costs on the mileage rate, tools, mixers and buckets, PPE, phone, bookkeeping software).
| Profit: £32,000 − £4,500 | £27,500 |
| Income Tax: (£27,500 − £12,570) = £14,930 × 20% | £2,986.00 |
| Class 4 NI: £14,930 × 6% | £895.80 |
| Real bill | £3,881.80 |
| Already deducted by contractors | £6,400.00 |
| Refund | £2,518.20 |
If Jay lived in Scotland, her Income Tax would be £2,957.82 (the 19% starter band), so the refund would be about £2,546. Even with no receipts at all she'd get about £1,608 back, using the £1,000 trading allowance, because of the Personal Allowance and the lower NI rate. Try your own figures in the calculator.
Expenses CIS workers can claim
Expenses lower your profit, and every £100 of expenses is worth £26 to a basic-rate subcontractor (20% tax + 6% NI). The rule is "wholly and exclusively for the business". Common ones:
- Materials you bought for jobs (if the contractor paid you for them, they're in your gross pay, so claim the cost here).
- Tools and equipment: hand and power tools, ladders, mixers, workwear with a logo, PPE (boots, hi-vis, hard hat), and repairs to them.
- Van or car: either the mileage rate (45p a mile for the first 10,000 business miles in 2025/26, 55p from 6 April 2026, 25p after that) or the real running costs plus capital allowances. Not both, and not your drive to a permanent workplace.
- Travel to temporary sites: parking, tolls, train fares, and food and lodging if you stay away overnight.
- Phone and internet (the business share), insurance (public liability, tools), trade cards and courses (CSCS, CPCS, Gas Safe), bank charges on a business account, accountant or software fees.
- Working from home: a flat £10–£26 a month depending on hours, if you do the admin at home.
Not allowed: everyday clothes, your normal commute, fines, and the personal share of anything. Keep the receipts for 5 years after the 31 January deadline. If your expenses are under £1,000, the £1,000 trading allowance instead is simpler (the calculator picks it for you).
How to claim it yourself
- Gather the year's statements. Every contractor must give you a monthly payment and deduction statement within 14 days of the end of each tax month. Add up the gross paid, the materials, and the CIS deducted. (See the prompt below to get ChatGPT, Gemini or Claude to total them.)
- Add up your expenses from receipts and bank statements, by type.
- Sign in to your Self Assessment account on gov.uk (you got a UTR when you registered for CIS) and start the return for the year.
- In the self-employment section, put your total pay before deductions as income, your expenses, and the total deductions in the box for CIS deductions. gov.uk's wording: "your total pay before deductions were taken, as 'income'" and "the total deductions contractors have taken, as 'CIS deductions'".
- Submit. The calculation at the end shows the refund. If it's a repayment, give your bank details on the return so it's paid straight to your account.
Once it's filed, use gov.uk's claim a tax refund page to check when to expect a reply. Refunds are held if the deductions you claim don't match what contractors reported to HMRC, so copy the figures from the statements exactly.
Stopped trading during the year? Sole traders and partners can claim deductions back for that year without waiting for the return: see "If you stop trading" on gov.uk.
A prompt to total your statements
Paste this into ChatGPT, Gemini or Claude with the text of your statements (or photos of them). Check the totals against the statements before you use them: AI can misread a photo.
Here are my CIS payment and deduction statements for the tax year 6 April 2025 to 5 April 2026. Make a table with one row per statement: contractor, tax month, gross amount paid, cost of materials, amount liable to deduction, CIS deducted. Then give totals for gross paid and CIS deducted, per contractor and overall. List any tax month from April to March with no statement from a contractor I worked for, and any line where the deduction isn't 20% (or 30%) of the amount liable. Don't guess missing figures: mark them MISSING. [paste statements]
If a contractor won't send your statements
Ask them first: they're legally required to give them to you. If they've gone bust or won't reply, gov.uk says to write to HMRC (PT Operations, HM Revenue and Customs, BX9 1BX) with your name, address and UTR, the contractor's name and address, their tax reference if you know it, the dates or tax months they paid you, and why you don't have the statements. Your bank statements showing the net payments help.
Traps that cost subcontractors money
- Leaving it to January. The refund is your money: file in the spring or summer and it arrives months earlier. Filing after 31 January also means a £100 penalty, even if HMRC owes you.
- Paying 30% for no reason. If your statements show 30%, you're not registered or the contractor can't match your details. Register for CIS (or give them the exact name and UTR you registered with) and it drops to 20%. The 30% still comes back on the return, but it's a bigger loan to HMRC.
- Deductions taken off materials or VAT. CIS is on labour only. Split labour and materials on every invoice, and keep material receipts: the contractor can ask for evidence and will estimate the cost if you don't have it.
- Paying a rebate firm a big cut. Some charge a percentage of the refund, or a fixed fee per return. Filing your own return is free. Pay for help when it's genuinely complicated: a loss, a partnership, several years behind, an HMRC enquiry.
- Not filing for back years. If you missed a year, you can generally still claim a refund for up to 4 years after it ended, but penalties may apply if HMRC asked for a return. File the missing years as soon as you can.
- Forgetting payments on account. If you owe more than £1,000 and less than 80% of your bill was covered by deductions and PAYE, HMRC also asks for advance payments towards next year. The calculator flags this.
- Student loans. If your income is over your plan's threshold, repayments are added to the return and reduce the refund. The calculator leaves them out.
Spend less time on the paperwork that gets you here. Our free Trades Skills turn ChatGPT, Gemini or Claude into an office manager for your trade: quote-builder writes proper quotes with labour and materials split, and payment-chaser chases the contractor who's late paying (or late with your statement). The free invoice maker shows the CIS deduction on labour only. Set-up takes about 3 minutes, no coding.
Bookkeepers with CIS clients: Bookkeeper Skills chases missing records and turns bank lines into client questions.
FAQ
How do I claim my CIS tax back?
File your Self Assessment return for the year. Put your total pay before deductions as income, your expenses, and the total CIS deductions from your statements in the CIS deductions box. HMRC takes the deductions off your bill and repays the rest.
How much CIS tax will I get back?
The deductions minus the Income Tax and Class 4 NI actually due on your profit. £32,000 gross, £6,400 deducted and £4,500 of expenses gives about £2,518 back for 2025/26 (outside Scotland). Use the calculator for your figures.
When can I claim it?
From 6 April after the tax year ends: 2025/26 refunds can be claimed now. The latest you can file without a penalty is 31 January 2027.
How long does a CIS refund take?
It depends on HMRC's checks. gov.uk's claim a tax refund page has a tool showing when to expect a reply. Mismatched deduction figures are the most common cause of delay.
Do I need an accountant or a rebate company?
No. Filing your own return on gov.uk is free. An accountant can be worth paying for if your records are a mess, you made a loss, you're in a partnership or several years behind, or HMRC has questions.
Is CIS taken off materials?
No: only the labour part. Not VAT, materials you paid for, plant hire or consumables. Show labour and materials separately on every invoice.
I'm a limited company. Can I use this?
No. A limited company offsets CIS deductions against the PAYE and NI it owes through its payroll (Employer Payment Summary) and can claim a repayment of the rest from HMRC. Ask your accountant.
This page is general information written by an AI agent and checked against gov.uk (CIS subcontractor guidance, Income Tax and Scottish Income Tax rates, National Insurance rates and allowances, payments on account and Self Assessment penalties) on 1 November 2026. It is an estimate, not tax advice: HMRC's calculation on your return is the one that counts. If you spot an error, please open an issue.