Claim CIS Tax Back: How UK Subcontractors Get Their CIS Rebate

By Pro Playbooks | September 2026 | Tax

Every payment you receive under the Construction Industry Scheme has already been taxed before it lands in your bank account. Your contractor takes a flat 20% off the labour on every invoice and sends it to HMRC, with no account taken of your personal allowance or a single expense you carried. That blunt deduction is why overpaying is the norm for registered subcontractors, and why a CIS rebate is not a bonus or a loophole. It is your own money coming back.

HMRC does not post the difference back automatically. You have to claim it, once a year, through a Self Assessment tax return. This guide covers how the deductions work, why most subbies are owed a repayment, how to claim CIS tax back yourself, and the upgrade that stops deductions at source.

CIS Deductions Explained: Why 20% Comes Off Every Invoice

Gov.uk's own Construction Industry Scheme pages describe the deductions as advance payments towards the subcontractor's tax and National Insurance. They are a deposit against a bill that has not been calculated yet, not a separate tax.

Before paying you for the first time, a contractor must verify you with HMRC, and there are only three possible answers:

• Deduct 20%. You are registered for CIS as a subcontractor. The standard rate, where most subbies sit.
• Deduct 30%. HMRC could not match you to a CIS registration. Pure lost cash flow until it is fixed.
• Deduct nothing. You hold gross payment status, covered later in this guide.

The deduction does not apply to the whole invoice. Under HMRC's CIS340 rules, the contractor removes any VAT you charged and the direct cost of materials you supplied, then applies the rate to what is left, essentially your labour. Invoice £2,000 made up of £1,400 labour and £600 of materials and a 20% deduction should be £280, not £400. Always split labour and materials on your invoices, because contractors get this wrong.

Every month you are paid under deduction, the contractor owes you a payment and deduction statement within 14 days of the end of the tax month. Tax months run from the 6th to the 5th, so statements are due by the 19th. These statements are the receipts for tax you have already paid and the evidence behind your claim. Treat them like money.

Who Gets a CIS Rebate, and Why

Your real Income Tax bill is worked out on profit, not turnover. Add up what you invoiced, take off your allowable expenses, then take off the personal allowance, which is £12,570 for the 2026/27 tax year. Only what remains is taxed, at 20% in the basic rate band, with self-employed Class 4 National Insurance at 6% on profits between £12,570 and £50,270.

The CIS deduction ignored all of that. It took 20% of your labour from the first pound, as if you had no allowance and spent nothing to earn your money. The personal allowance alone is worth £2,514 of overpaid tax to a typical 20%-rate subbie, and every £1,000 of allowable expenses cuts the true bill by roughly £260 more at basic rate levels.

A worked example using 2026/27 rates: a groundworker invoices £36,000 of labour, so his contractors deduct £7,200 across the year. His records total £7,000 of expenses: mileage, tools, PPE, phone, insurance. Taxable profit is £29,000, and after the allowance his Income Tax and Class 4 come to £4,271.80. He has already paid £7,200 through deductions, so his refund is £2,928.20. Nearly three grand, in one ordinary year, at an ordinary income.

One exception worth knowing: subbies with profits pushing past £50,270, or a lot of other income, can find the higher rate band eats into the effect and can even owe more rather than less. That is a minority. For the standard-rate subbie, the arithmetic bends firmly toward repayment.

How to Claim CIS Tax Back: The Self Assessment Route

The claim is one online form, filed once a year. Here is the route in order.

1. Get registered properly

Register for Self Assessment as a sole trader on gov.uk, which issues your Unique Taxpayer Reference, by 5 October after the end of the tax year you started working for yourself. Then register separately for CIS as a subcontractor, because without that second registration contractors are told to deduct 30% instead of 20%. Use exactly the same name details HMRC holds for you, since mismatched details are the top cause of failed verifications.

2. Gather three numbers

You need your gross turnover for the year, your total allowable expenses, and the total deductions from your statements. The two classic errors both live here. Turnover must be gross: if you invoiced £36,000 and banked £28,800 after deductions, turnover is £36,000, not the banked figure. And the CIS box wants the tax deducted from your statements, not your gross pay and not what you received.

3. File, and file early

The return for a tax year opens on 6 April and the online deadline is the following 31 January. A refund claim filed in April or May is processed in HMRC's quietest season and the money can be back within weeks; the identical claim filed in the January crush joins the longest queue of the year. Missing the deadline triggers an automatic £100 penalty even when HMRC owes you.

Inside the return, enter your gross turnover, your expenses (a single total figure is acceptable if turnover is under the VAT threshold), and then the CIS deductions box: box 38 on the SA103S paper short pages, or online the question in the self-employment section about CIS deductions taken from your payments. This entry is your claim. Get it right to the pound.

Before submitting, the service shows your calculation, and for most readers the final line says amount overpaid. Give your bank details for direct transfer, submit, and save the receipt. Straightforward, well-matched claims are often repaid within a few weeks, though some are held for security checks first, which is normal and not an accusation. Track the repayment in your online account; if it genuinely stalls, the Self Assessment helpline on 0300 200 3310 can see the hold and say what is needed to release it.

The Records That Grow the Rebate

Expenses are where refunds are won and lost, and HMRC's test is that a cost must be incurred wholly and exclusively for the trade. The big categories for a working subbie:

• Mileage and travel. Business miles at the approved rates of 45p a mile for the first 10,000 miles and 25p after, plus tolls and parking. For most subbies moving between temporary sites this is the biggest line, and the only evidence needed is a mileage log.
• Tools and equipment. Hand and power tools, blades and bits, repairs, servicing and hire.
• Materials and consumables you bought and supplied for jobs, plus the fixings and sundries that vanish into every job.
• PPE and protective workwear. Boots, hard hats, hi-vis, gloves and genuinely protective gear. Ordinary clothes never qualify.
• Phone and admin. The business share of your mobile and broadband, public liability and tool insurance, software, and a home office claim for evening paperwork.
• Training and subscriptions that keep your existing trade skills current, including cards, tickets and renewals.

What never qualifies: everyday meals, fines of any kind, entertaining, and clothing that is not protective or branded. Keep the records behind every claim for at least five years after the 31 January filing deadline; a clear photo of a receipt is as good as the paper. Ten minutes a week filing photos and logging miles is the entire discipline, and it is the same digital habit Making Tax Digital will soon require anyway. The full trades expenses checklist, with the grey areas and the records each category needs, is laid out line by line in our CIS refunds playbook.

Why Give a Rebate Firm a Fifth of Your Own Money?

An entire industry exists to file this one return for you, and plenty of firms charge a percentage of your refund, in some cases up to 20% of it, sometimes with VAT on the fee and a minimum charge on top. On the £2,928.20 refund above, a firm on 20% takes £585.64. The boxes they fill in are the same boxes you can fill in, the calculation is run by the same HMRC engine, and there is no special agent channel that produces bigger refunds from the same figures.

Two protections to know. Never hand any firm your Government Gateway sign-in, which is against HMRC's rules for agents in any case, and prefer arrangements where HMRC pays the repayment directly to you rather than through the firm's account. There are genuinely complicated years, such as mixed CIS and PAYE income with rental on top, where a proper accountant on a transparent flat fee makes sense. For a standard subbie year, the return is an evening's work once you have a decent walkthrough, and the box-by-box walkthrough in the book costs less than a takeaway.

One more thing rebate adverts never mention: the claim windows are measured in years, not days. A return can be amended up to 12 months after its filing deadline, and beyond that a claim for overpayment relief can go back up to four years from the end of the tax year concerned. Every spring, one more unclaimed year expires permanently, so deal with the past while the window is open.

Gross Payment Status: The Upgrade That Ends Deductions

There is a version of CIS where nothing is taken at all. With gross payment status, contractors are told to deduct 0% and you are paid in full, settling your own tax through Self Assessment. On £3,000 of monthly labour, that is £600 a month staying in your account instead of sitting with HMRC until the year-end reconciliation.

HMRC grants it to subcontractors who pass three tests: a business test (you do construction work in the UK and run it through a bank account), a turnover test (net construction turnover of at least £30,000 for a sole trader, excluding VAT and materials), and a compliance test, the one that decides most applications: returns filed on time and tax paid on time. Sole traders apply online through the CIS service with their Government Gateway account.

Be clear about what it is not: a tax cut. The same profit produces the same bill, except nothing was paid in advance, so January brings a real bill instead of a refund. It suits the established subbie with steady turnover and the discipline to move a slice of every payment into a tax pot the day it lands.

Frequently Asked Questions

How do I claim CIS tax back?

Through a Self Assessment tax return. Register for Self Assessment and CIS, then after 5 April file the return online: enter your gross turnover, your allowable expenses and the total CIS deductions from your payment and deduction statements. HMRC calculates what you truly owed, sets your deductions against it, and repays the difference to your bank account.

How is a CIS rebate calculated?

Your true bill is worked out on profit: turnover minus allowable expenses, minus the £12,570 personal allowance for 2026/27, with the rest taxed in bands plus Class 4 National Insurance. That bill is compared with the 20% already deducted from your labour. Because the deduction ignored your allowance and expenses, the deductions usually exceed the bill, and the excess is your rebate.

What are CIS deductions and why is 20% taken?

Contractors deduct tax at source from payments to subcontractors and send it to HMRC as an advance payment towards your Income Tax and National Insurance. Registered subcontractors are deducted at 20%, unregistered at 30%, and gross payment status holders at 0%. The deduction applies to your labour after VAT and the cost of materials you supplied are removed.

What allowable expenses can a CIS subcontractor claim?

Anything incurred wholly and exclusively for the trade: business mileage at the approved rates, tools and equipment, materials you supplied, PPE and protective workwear, the business share of your phone, public liability and tool insurance, training that keeps existing skills current, and home office admin. Ordinary clothes, everyday meals, fines and entertaining are not allowable.

What is gross payment status for CIS?

The 0% CIS rate: contractors pay you in full with no deductions and you settle your own tax through Self Assessment. To qualify you pass three tests: a UK construction business run through a bank account, net construction turnover of at least £30,000 for a sole trader, and a clean record of filing and paying on time. It transforms cash flow, but it is not a tax cut.

Related Reading

• How to price a job as a tradesman
• Making Tax Digital for sole traders: what is changing and when
• Getting a mortgage when you are self-employed in the UK

This article explains the Construction Industry Scheme rules as they stand for the 2026/27 tax year. It provides general information, not tax or financial advice. Your circumstances may differ; check current figures on gov.uk or speak to a qualified accountant about your own position.