Every year thousands of subbies overpay tax and never claim it back. Here's how CIS actually works, in plain language.
Checked August 2026 on official sources. Registering is FREE and drops you from 30% to 20% immediately. And the deducted money is not lost — it's tax paid in advance. Your first £12,570 a year is tax-free, so most subbies overpay during the year and get a refund back.
You register with HMRC yourself, free — you'll need your UTR number (from registering as self-employed). Until you register, contractors must deduct 30% instead of 20%. Ten minutes on gov.uk saves you a tenth of every payment.
Your contractor must give you a payment and deduction statement every month — keep them all, they are the proof of tax you already paid. Keep receipts too: tools, fuel, PPE, van, phone. Expenses cut your tax bill and grow your refund.
CIS takes 20% of everything, but your first £12,570 is tax-free — so most subbies pay too much during the year. The overpaid tax comes back after you file your Self Assessment return. Straightforward refunds usually land in your bank in 3–6 weeks.
«Refund agents» often take a big cut of YOUR refund for filling in a form — a normal accountant charges a fixed fee, or you can file yourself on gov.uk. Never give anyone your Government Gateway login. And if your gross income is over £50,000, Making Tax Digital applies since April 2026 — digital records and quarterly updates.
Every situation is a bit different — write to us and we'll point you the right way, honestly and free. And your free Graftum member account includes a work diary: days worked, money earned, money still owed to you.
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