CIS Tax Refunds for UK Subcontractors — How to Claim Back Overpaid CIS Deductions (2026)

Why so many CIS subcontractors overpay

Under CIS, a contractor who pays you for construction work is legally required to deduct tax from your labour at source and hand it to HMRC on your behalf. For most registered subcontractors that deduction is 20% of the labour element of every invoice. If you're not registered with CIS at all, the contractor deducts 30%.

Here's the catch: that 20% is taken off your gross labour, before you've deducted a single penny of business expenses and before you've used any of your tax-free personal allowance. But the tax you actually owe is worked out on your profit — turnover minus allowable costs — and only the portion above the personal allowance is taxed at all. Because the deduction ignores your costs and your allowance, the amount taken at source is almost always more than your real liability. The gap is your refund.

Think about a typical groundworker, electrician or plasterer with thousands of pounds a year in tools, fuel, materials, insurance, protective clothing, accountancy fees and mileage. None of that has been factored in when the 20% came off. The more you spend running your trade, the bigger the overpayment tends to be.

CIS deductions are a payment on account — not a final tax

The single most important thing to understand is that CIS deductions are not a separate tax. They are an advance payment towards the income tax and National Insurance you'll owe at the end of the year. HMRC treats every pound deducted under CIS as money already paid into your tax account.

So at the end of the tax year you (or your accountant) calculate your real liability based on profit. Then you subtract everything already paid through CIS. If the CIS deducted is more than your bill — which it usually is — HMRC owes you the difference. If it's less, you pay the balance. The CIS deduction is simply a credit sitting against your account, waiting to be reconciled.

Sole traders: claim through Self Assessment

If you operate as a sole trader (or as a partner in a partnership), you reclaim overpaid CIS through your Self Assessment tax return. There is no separate "CIS refund form" — it's all handled inside the return.

On the self-employment pages you report your full turnover (the gross figure your contractors paid you, before deductions) and all your allowable expenses, which gives your taxable profit. There is then a specific box for the total CIS deductions taken from your payments during the year. HMRC works out the income tax and Class 4 National Insurance due on your profit, then offsets the CIS already deducted against that figure.

If the CIS deducted exceeds your income tax and Class 4 NIC liability for the year, the surplus is repaid to you — or, if you prefer, set against the next payment on account. You file the return after the tax year ends on 5 April, and the sooner you file, the sooner the refund is processed. You don't need to wait until the January deadline.

Limited companies: offset CIS suffered against your PAYE bill

If you run your subcontracting through a limited company, the mechanism is completely different — and getting it wrong is a common, expensive mistake. A company cannot reclaim CIS through the corporation tax return, and the directors cannot put company CIS on their personal Self Assessment.

Instead, the CIS deducted from your company ("CIS suffered") is offset against the amounts your company owes HMRC as an employer — PAYE, employee and employer National Insurance, and any CIS you yourself deduct from sub-subcontractors. You report the CIS suffered each month on your Employer Payment Summary (EPS) through your payroll software. HMRC then reduces what your company has to pay over for the month by that amount.

If your company has suffered more CIS than its total PAYE/NIC/CIS liabilities across the whole tax year, the excess can't be used up in-year. After the tax year ends (from 6 April, once your final EPS and payroll submissions are in), you write to or apply to HMRC to have the remaining balance repaid or reallocated against other taxes such as corporation tax or VAT. This is why running an accurate payroll and submitting the EPS every month matters so much for subcontracting companies.

Worked example: a sole trader subbie owed a refund

Let's run the numbers for a self-employed bricklayer working under CIS during the 2025/26 tax year. Figures are illustrative and rounded for clarity.

• Gross labour invoiced to contractors: £45,000
• CIS deducted at 20% on that labour: £9,000 (paid to HMRC at source)
• Allowable business expenses (tools, van running costs, insurance, accountant, materials, PPE): £11,000
• Taxable profit: £45,000 − £11,000 = £34,000
• Personal allowance: £12,570 (tax-free)
• Profit subject to income tax: £34,000 − £12,570 = £21,430 at 20% = £4,286
• Class 4 NIC on profit above the threshold (roughly): £1,600
• Total tax and Class 4 NIC due: about £5,886

Now the reconciliation. Our bricklayer has already had £9,000 taken under CIS, but his actual liability is only around £5,886. HMRC offsets the £9,000 already paid against the £5,886 owed and refunds the difference — a refund of roughly £3,100. That money was overpaid purely because the 20% came off before his expenses and personal allowance were taken into account. This is a typical outcome, not an unusual one.

Sole trader vs limited company: how the refund works

What records you need to claim

Whether you're a sole trader or a company, your claim is only as good as your paperwork. The deductions figure you report must match what HMRC has on record, so keep the following safe through the year:

• CIS payment and deduction statements from every contractor who paid you. By law, a contractor must give you a statement within 14 days of the end of each tax month showing your gross pay, materials, and the CIS deducted. These are your proof of how much has already been paid to HMRC.
• Your sales invoices, showing labour and materials split out clearly. CIS is only deducted from labour — if materials aren't separated, a contractor may wrongly deduct from the whole lot.
• Expense records and receipts for everything you're claiming — tools, fuel and mileage, vehicle costs, insurance, accountancy, subcontractors, PPE, phone, and use-of-home. Bigger genuine expenses mean a bigger refund.
• Bank statements reconciling the net amounts you actually received against your invoices.

If a contractor never sent you a statement, chase them — you're entitled to it. As a fallback, your bank records of the net payments plus your own invoices let you reconstruct the deduction, but a proper statement is far cleaner. Tools like Trade2Base make this easier by tracking every job's income and the deductions taken across the year, so you reach 5 April with the totals already to hand instead of digging through a shoebox.

How long does a CIS refund take?

For sole traders, once you've filed an accurate Self Assessment return showing a repayment due, HMRC typically processes straightforward refunds within a few weeks — often around 2 to 6 weeks if there are no queries and your bank details are set up for repayment. File early in the tax year (April to June) and you usually get paid faster than the January rush, when HMRC is processing millions of returns at once.

For limited companies reclaiming a year-end surplus, repayments tend to take longer — frequently 6 to 12 weeks or more — because HMRC reconciles your payroll submissions, EPS figures and employer account before releasing funds. Submitting clean monthly EPS reports throughout the year is the best way to keep this moving.

Common reasons CIS refunds get delayed

Most delayed refunds come down to a handful of avoidable problems:

• Wrong or mismatched UTR: if the Unique Taxpayer Reference your contractor used doesn't match your records, HMRC may not be able to link the deductions to your account. Check your UTR is correct on every statement.
• Missing deduction statements: if the figure you claim doesn't reconcile with what contractors have reported, HMRC will hold the refund until it's resolved.
• Security and compliance checks: HMRC routinely selects CIS repayments for additional checks to combat fraud. A genuine claim with good records will pass, but it adds weeks. Don't panic if you're asked for evidence — just supply it promptly.
• No repayment bank details on file: if HMRC can't pay you directly, the refund may issue as a slower payable order.
• Limited company directors claiming on the wrong return: putting company CIS on a personal return causes mismatches and delays.

Gross payment status: stop the deductions altogether

If you're consistently getting large refunds, it may be worth applying for gross payment status. With gross status, contractors pay you in full with no CIS deducted at source — you simply account for all your tax through Self Assessment or corporation tax at the year end. That keeps the cash in your business through the year instead of parked with HMRC.

To qualify, HMRC applies three tests: a business test (you do construction work in the UK and run it through a business bank account), a turnover test (broadly £30,000 of net construction turnover per relevant person), and a compliance test (your tax affairs and returns are up to date). Gross status improves cash flow significantly, but it puts the full responsibility for paying your tax on you — so only go for it if your record-keeping and discipline are solid.

Beware CIS refund claim companies

You'll see adverts from firms promising to "get your CIS tax back" with no upfront fee. Be careful. Many of these claim companies take a hefty cut — often 20% to 40% of your refund, sometimes plus a flat fee — for filing a return you could file yourself or have an accountant do for a fixed price. Some have signed clients up to assignments that hand the firm control of all future repayments, not just the one claim.

A reputable local accountant who specialises in trades will usually prepare your Self Assessment and reclaim your CIS for a fixed annual fee that's a fraction of what a percentage-based claim company keeps. Always check exactly what you're signing, who the refund is paid to, and whether you're authorising the firm to handle anything beyond the single claim in front of you.

The best fix: don't overpay in the first place

A refund is nice, but it's your own money coming back after sitting interest-free with HMRC for up to a year. The smarter play is to keep your records tight so you capture every allowable expense, claim on time, and — if the overpayments are consistently large — apply for gross payment status to stop the leak at source.

That all hinges on knowing your numbers. If you track every job's income, the labour-versus-materials split, the CIS deducted, and your running expenses as you go, the refund claim becomes a five-minute reconciliation instead of a year-end scramble. Trade2Base helps subcontractors see their income clearly across the year — and which marketing channels are actually bringing in the paid jobs — so nothing falls through the cracks at tax time.