CIS refunds — how subcontractors claim back overpaid tax

Updated: 14/07/2026 · 7 min read

Under the Construction Industry Scheme (CIS), contractors deduct tax at source from subcontractors’ pay — 20% if you are registered, 30% if not — and pass it to HMRC. Because the deduction ignores your personal allowance and expenses, most subcontractors overpay through the year and claim the difference back through Self Assessment.

How the deduction works

The contractor pays you net of CIS tax on the labour element (materials you invoice are not deducted) and must give you a monthly payment and deduction statement. The deduction is an advance on your income tax and National Insurance — not an extra tax.

Registered subcontractor: 20% deduction
Unregistered: 30% (registering pays for itself immediately)
Gross payment status: 0% deducted for qualifying businesses

Why a refund is usually due

20% is taken off your whole labour income from the first pound. Your actual tax is calculated on profit — after the personal allowance and after expenses like tools, materials, van costs, PPE and insurance. The gap between what was deducted and what is actually due comes back to you.

Claiming it back, step by step

Gather all monthly CIS statements (they prove your total deductions)
Gather receipts and invoices for every expense — each documented cost increases the refund
File your Self Assessment for the tax year
HMRC offsets deductions against the tax due and repays the difference

What makes refunds bigger (and faster)

Complete CIS statements — a missing month understates your deductions
Complete expense evidence — undocumented costs are unclaimable
Filing early — refunds are processed sooner after 6 April
Clean digital records — fewer HMRC queries, faster payout

Keep it all in one place

CIS statements and expense receipts scattered across a year of van dashboards are the number one refund killer. Photograph or email documents into one system as they arrive — everything is extracted, categorised and export-ready for the return, and your accountant sees it live.

Every receipt captured, categorised and audit-ready.

Snap a photo or forward the email — Reclaim Day reads the vendor, amounts, VAT and date for you.

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Frequently asked questions

How much CIS refund will I get?+

It depends on deductions and expenses, but the mechanics are simple: refund = CIS deducted minus tax actually due on your profit. More documented expenses → lower profit → bigger refund.

When can I claim my CIS refund?+

After the tax year ends on 5 April, by filing your Self Assessment. Filing early usually means an earlier repayment.

What if I lost some CIS statements?+

Ask the contractor for copies — they are required to provide them. Your own records of payments received help cross-check the totals.

Why am I being deducted 30% instead of 20%?+

You are not registered as a CIS subcontractor, or the contractor could not verify you. Register with HMRC using your UTR — the difference is 10% of every payment.

This guide is general information, not tax advice. Rules and figures change — check gov.uk (HMRC) for current rates, and speak to an accountant about your situation.