How to get a CIS refund (and stop lending HMRC your money)

Published May 2026 · 7 min read

CIS deductions are tax paid early, at a flat rate, before anyone knows what your actual profit is. Your real tax bill is worked out later, on your Self Assessment, after your personal allowance and expenses are taken off. Because the flat deduction ignores both, many subcontractors end the year having paid more than they owe — and that difference comes back as a refund.

Why refunds happen

Say you’re deducted 20% on all your labour. But your first £12,570 of profit is covered by the personal allowance and taxed at 0%. And your profit is your income minus expenses — tools, materials, mileage, insurance, phone. The 20% was taken off the lot. The gap between “tax deducted on everything” and “tax due on profit after allowances” is your refund. If you were on the 30% unregistered rate, the overpayment is usually bigger still — see CIS deductions explained.

Worked example

• Labour invoiced over the year: £40,000, all deducted at 20% → £8,000 CIS paid.
• Allowable expenses: £9,000 → taxable profit £31,000.
• Income Tax: (£31,000 − £12,570) × 20% = £3,686. Class 4 NI at 6% on the same slice adds about £1,106.
• Total due ≈ £4,792. CIS already paid £8,000. Refund ≈ £3,200.

Figures are illustrative and use 2026/27 thresholds — your own numbers will differ, and your accountant should confirm your position.

How to actually claim it

For sole traders there is no separate “CIS refund form” — the refund happens through your Self Assessment tax return:

• File your return any time after the tax year ends on 5 April — you don’t have to wait until the 31 January deadline.
• Enter your income, expenses and the total CIS deducted (from your payment & deduction statements).
• If you’ve overpaid, HMRC repays the difference — typically within a few weeks of filing, direct to your bank.

The single biggest cause of delayed or shrunken refunds is missing evidence: lost deduction statements and unclaimed expenses. No statement, and you may struggle to prove the tax was ever taken; no receipts, and your profit looks higher than it really was.

The records that protect your refund

• Every payment & deduction statement. Due from the contractor by the 19th of each month. Photograph it and store it the day it arrives.
• Every expense receipt. Materials, fuel, tools, PPE, insurance — each one lowers taxable profit and raises the refund.
• Bank statements. They tie the story together and catch expenses you forgot to log.

File early, get paid early

Refunds go to those who file first. If HMRC owes you money, every month you delay filing after 5 April is another month of an interest-free loan from you to the government. Subbies with tidy records often file in April or May and see the refund before summer.

Common questions

I was deducted 30% — do I lose the extra?

No. Every pound deducted counts, whatever the rate. But register for CIS anyway: 20% all year is far kinder to your cash flow.

What if I can’t find a statement?

Ask the contractor for a copy — they must keep records and it’s their duty to provide statements. Your own log of payments received (and the bank lines showing them) is strong supporting evidence.

Does a refund mean I did something wrong?

Not at all — it’s built into how flat-rate deductions work. The only mistake is not claiming everything you’re entitled to.

A timeline that works

• All year: photograph every deduction statement and every receipt the day you get them; log mileage as you drive it.
• Early April: the tax year ends on the 5th. Check your Annual Return — income, expenses, mileage and total CIS deducted should already be complete.
• April–May: your accountant reviews and files. Because everything is evidenced, there’s nothing to reconstruct.
• A few weeks later: the repayment lands. Compare that with the subbies still hunting receipts in December.

One more habit worth the thirty seconds: when a contractor pays you, check the deduction on the remittance matches what later appears on the monthly statement. Discrepancies are far easier to fix in the month they happen than at year end — and your WhatsApp thread with SubReady gives you a dated record of every statement the moment you sent it.

Keep every deduction and every receipt captured the moment it happens, and the refund largely takes care of itself. That’s exactly what bookkeeping on WhatsApp is for.