CIS Tax Refund for Construction Workers (2026-27)

If you're a construction worker in the UK and your contractor has been deducting tax from your pay under the Construction Industry Scheme (CIS), there's a good chance you're owed money back. Most subcontractors overpay tax during the year because CIS deductions are taken at a flat rate—either 20% or 30%—without accounting for your Personal Allowance, business expenses, or actual tax liability. When you file your Self Assessment tax return, HMRC reconciles what you've paid against what you actually owe, and the average CIS refund sits between £2,000 and £3,000. This guide walks you through how CIS works, why refunds happen, what expenses you can claim, and exactly what you need to do to get your money back for the 2026-27 tax year.

What is the Construction Industry Scheme (CIS)?

The Construction Industry Scheme is HMRC's way of collecting tax from people working in construction. If you're a subcontractor—a self-employed tradesperson like a bricklayer, electrician, plasterer, or labourer—your contractor (the business paying you) must register with CIS and deduct tax from your payments before they pay you.

The contractor sends this deducted tax straight to HMRC on your behalf, then gives you a payment statement showing:

• Your gross payment (the full amount before deductions)
• How much CIS tax was deducted
• Your net payment (what you actually received)

These deductions are not your final tax bill. They're advance payments toward your eventual tax liability. At the end of the tax year (which runs 6 April to 5 April), you file a Self Assessment tax return to work out your real tax bill. If the CIS deductions exceed what you actually owe, HMRC refunds the difference.

CIS deduction rates for 2026-27

There are two rates:

• 20% for registered subcontractors: If you've registered with HMRC for CIS, contractors deduct 20% from your labour payments (materials are usually paid gross, without deduction).
• 30% for unregistered subcontractors: If you haven't registered, the deduction jumps to 30%. This is a significant penalty for not registering, so it's always worth doing.

Example: Tom is a registered plasterer. He invoices a contractor £5,000 for a job (£4,000 labour, £1,000 materials). The contractor deducts 20% from the £4,000 labour = £800. Tom receives £4,200 (£5,000 minus £800). The contractor sends the £800 to HMRC and gives Tom a payment statement.

Why do CIS workers usually get refunds?

CIS deductions are blunt instruments. They're calculated on your gross labour payments without considering:

1. Your Personal Allowance: For 2026-27, everyone gets the first £12,570 of income tax-free. If your total earnings are below or close to this threshold, you may owe little or no tax, yet CIS has already taken 20% or 30%.

2. Business expenses: As a self-employed subcontractor, you can deduct legitimate business costs—tools, vehicle expenses, protective clothing, training, insurance, accountancy fees—from your income before calculating tax. CIS deductions ignore these entirely.

3. Other income and reliefs: Your actual tax bill depends on your total income from all sources, any pension contributions, and other reliefs. CIS deductions are taken in isolation, job by job.

Because of these factors, most subcontractors find they've overpaid. The average refund is £2,000 to £3,000, though it varies widely depending on earnings and expenses.

Example: Sarah is a self-employed carpenter. Over the 2026-27 tax year, she earns £35,000 in labour payments. Contractors deduct 20% CIS = £7,000 sent to HMRC. Sarah has £6,000 in allowable business expenses (van costs, tools, insurance, accountancy). Her taxable profit is £35,000 – £6,000 = £29,000. After her Personal Allowance (£12,570), her taxable income is £16,430. Tax due: £16,430 × 20% = £3,286. She's already paid £7,000 via CIS, so HMRC owes her a refund of £3,714.

Who qualifies for a CIS refund?

You're likely due a refund if:

• You're a self-employed subcontractor in construction and contractors have deducted CIS tax from your payments.
• Your total income for the year is relatively modest, or you have significant business expenses.
• You haven't yet filed a Self Assessment return for the tax year in question.

You must be registered as self-employed with HMRC. If you're not, you need to register before you can file a tax return and claim back overpaid tax.

Allowable business expenses you can claim

One of the biggest reasons CIS workers get refunds is claiming back expenses. HMRC allows you to deduct costs that are "wholly and exclusively" for your business [ITTOIA 2005 s. 34]. Common allowable expenses for construction subcontractors include:

Tools and equipment

Hammers, drills, saws, ladders, scaffolding, power tools—anything you need to do your job. If a tool costs over a certain threshold and lasts several years, you may need to claim capital allowances instead, but most hand tools qualify as day-to-day expenses.

Vehicle and travel costs

If you use your van or car for work, you can claim either:

• Actual costs: fuel, insurance, repairs, MOT, road tax, depreciation (proportioned for business use if you also use the vehicle privately), or
• Simplified mileage: 45p per mile for the first 10,000 business miles, 25p thereafter (2026-27 rates).

You cannot claim commuting from home to a permanent workplace, but travel between job sites, to suppliers, or to temporary workplaces is allowable.

Protective clothing and uniforms

Hard hats, steel-toe boots, hi-vis jackets, gloves. Ordinary clothing (like jeans or a plain t-shirt) doesn't count, even if you only wear it for work.

Training and professional development

Courses to update or improve skills relevant to your current trade (e.g., a health and safety refresher, new wiring regulations for electricians). Training to learn an entirely new trade generally isn't allowable.

Insurance

Public liability insurance, professional indemnity, tool insurance.

Accountancy and tax fees

Fees you pay to an accountant or tax adviser to prepare your Self Assessment return and manage your books.

Phone and internet

If you use your mobile or broadband for business (arranging jobs, ordering materials), you can claim the business proportion.

Subscriptions and licenses

Trade body memberships, CSCS card fees, professional licenses.

Small equipment and consumables

Nails, screws, sandpaper, cleaning materials for tools, small disposable items.

Accommodation and subsistence

If you work away from home temporarily (not permanently), you may be able to claim hotel costs and meal expenses, though HMRC's rules here are strict [EIM31810].

What you cannot claim:

• Personal expenses (your normal clothes, personal mobile calls, food when working locally).
• Fines or penalties.
• Costs reimbursed by your contractor.
• Entertainment or socialising.

Example: Liam is a self-employed electrician. In 2026-27 he claims: £1,200 tools, £3,500 van expenses (fuel, insurance, repairs), £400 protective clothing, £300 training course, £250 accountancy fees, £180 CSCS card and trade membership. Total expenses: £5,830. These reduce his taxable profit and increase his refund.

How to claim your CIS refund: step-by-step

1. Register as self-employed

If you haven't already, register with HMRC as a sole trader. You must do this by 5 October after the end of the tax year in which you started self-employment. For the 2026-27 tax year (ending 5 April 2027), that's 5 October 2027. Register online at gov.uk or call HMRC.

2. Register for CIS (if you haven't)

Registering for CIS as a subcontractor means contractors deduct 20% instead of 30%. You can register online via your Government Gateway account. You'll need your Unique Taxpayer Reference (UTR), National Insurance number, and some business details.

3. Keep records throughout the year

Save every payment statement your contractors give you (these show CIS deductions). Keep receipts, invoices, and bank statements for all business expenses. HMRC requires you to keep records for at least five years after the 31 January submission deadline [TMA 1970 s. 12B].

4. File your Self Assessment tax return

The deadline for online Self Assessment for the 2026-27 tax year is 31 January 2028. You'll need to complete:

• The main SA100 return
• The self-employment pages (SA103S for short self-employment or SA103F for full)
• The CIS deduction section, where you enter the total CIS suffered (from your payment statements)

HMRC's system will calculate your tax bill, deduct what you've already paid via CIS, and show any refund due.

5. Receive your refund

If you're owed money and your return is filed correctly, HMRC typically pays refunds within a few weeks. They'll send it to your bank account (make sure your details are up to date) or by cheque if no account is registered.

Common mistakes that delay or reduce refunds

Not registering as self-employed or for CIS

If you're not registered, you can't file a return or claim a refund. Worse, if you're unregistered for CIS, you're losing 10% of every payment to higher deductions.

Missing or incorrect CIS deduction figures

You must enter the exact total of CIS deducted, as shown on your payment statements. If you estimate or guess, HMRC's records won't match and they'll query your return, delaying your refund.

Claiming non-allowable expenses

Claiming personal costs, or expenses that aren't "wholly and exclusively" for business, can trigger an enquiry. HMRC may disallow the expense, reduce your refund, and charge penalties if they think you've been careless or deliberate.

Missing the deadline

File late and you'll face an automatic £100 penalty, even if you're due a refund. Further penalties accrue the longer you delay.

Not keeping records

If HMRC opens an enquiry and you can't provide receipts or evidence for your expenses, they'll disallow them. Always keep paperwork.

Mixing personal and business finances

Use a separate bank account for business income and expenses. It makes record-keeping much easier and looks more professional if HMRC asks questions.

What contractors must do: CIS300 monthly returns

Your contractor has obligations too. Each month, they must file a CIS300 return with HMRC, reporting:

• Payments made to subcontractors
• CIS deductions taken
• Subcontractors' details

They must also give you a payment statement (often called a CIS voucher or deduction statement) each time they pay you, or at least monthly. These statements are your proof of CIS deductions. If a contractor doesn't provide them, chase them up—without these, you can't prove what's been deducted and your refund claim will stall.

Contractors pay the deducted CIS tax to HMRC by the 22nd of the following month (19th if paying by post). This money sits with HMRC in your name until you file your Self Assessment and reconcile it.

What if you're employed, not self-employed?

If you're an employee (on PAYE), CIS doesn't apply to you. Your employer deducts Income Tax and National Insurance through PAYE, and you'd only get a refund by contacting HMRC directly (for example, if you've overpaid because you didn't work a full year). CIS is specifically for self-employed subcontractors.

Some workers are wrongly classified. If you think you should be employed but are being treated as self-employed (and having CIS deducted), this is worth investigating—HMRC has strict tests for employment status [ESM0500]. Being genuinely self-employed means you control how, when, and where you work, provide your own tools, and can send a substitute. If your "contractor" controls you like an employer, you may have been misclassified, with implications for your rights and tax.

National Insurance and CIS

CIS deductions cover Income Tax only, not National Insurance. As a self-employed person, you'll also owe:

• Class 2 NIC: £3.45 per week for 2026-27 if your profits are above £6,725 (collected via Self Assessment).
• Class 4 NIC: 6% on profits between £12,570 and £50,270, and 2% on profits above £50,270 (2026-27 rates).

These are calculated and collected when you file your Self Assessment. They don't affect your CIS refund directly, but they do reduce it slightly because they're added to your total bill.

Example: Returning to Sarah the carpenter: her tax bill was £3,286. She also owes Class 2 NIC (£3.45 × 52 weeks = £179.40) and Class 4 NIC on £16,430 profit (£16,430 × 6% = £985.80). Total tax and NIC: £3,286 + £179.40 + £985.80 = £4,451.20. CIS deducted: £7,000. Refund: £7,000 – £4,451.20 = £2,548.80.

How far back can you claim?

You can claim CIS refunds for up to four years after the end of the relevant tax year. For example, in 2026-27 you could still claim for 2022-23, 2023-24, 2024-25, and 2025-26 if you haven't already filed those returns. After four years, you lose the right to claim [TMA 1970 s. 43].

If you've been working in construction for several years and never filed Self Assessment, you could be owed thousands. However, you'll need to reconstruct your records—payment statements, bank statements, expense receipts—for each year. This can be time-consuming, but it's often worth it.

What to do next

If your situation is straightforward and you're comfortable with numbers, you can file your Self Assessment yourself using HMRC's online service or commercial software. Make sure you have:

• All your CIS payment statements
• A full list of business expenses with receipts
• Your UTR and Government Gateway login

If you have questions or want to check your specific circumstances, chat with AI Tax at myaitax.info. You can ask about which expenses apply to you, how to calculate your refund, or clarify any part of the CIS process. The AI assistant has access to HMRC manuals and current tax rules, and can give you tailored guidance in plain English.

If you'd rather hand the whole thing over to a professional, AI Accountant (also at myaitax.info) offers end-to-end service: they'll gather your records, calculate your expenses, file your Self Assessment, and handle any HMRC queries. This is especially useful if you've got multiple years to catch up on, complex expenses, or you simply want peace of mind that it's done right.

Don't leave money on the table. If you've had CIS deductions, you're very likely owed a refund—often a substantial one. The process is straightforward once you understand it, and the average £2,000–£3,000 refund is well worth an afternoon of paperwork or a small accountancy fee.