If you're a subcontractor in the Construction Industry Scheme, contractors deduct 20% from your labour payments (30% if you're not properly registered) and send it to HMRC as advance tax. Here's the thing that scheme design quietly guarantees: 20% off the top of gross labour is almost always more tax than you actually owe.

Why the maths lands in your favour

The deduction ignores everything that reduces your real bill: your £12,570 personal allowance, your van and mileage, tools, materials you supplied, insurance, phone — all of it. Real example shape: £48,000 of gross labour has £9,600 deducted at source. After the personal allowance and, say, £6,000 of legitimate expenses, the actual tax-and-NI bill is nearer £8,000. That's a £1,600 refund sitting with HMRC until you file. Four-figure refunds are the norm, not the exception, for subbies with a van and tools.

How to get it back

  1. Keep every CIS deduction statement — contractors must give you one for each payment month. Chase missing ones now, not in January; they're your proof.
  2. Claim every allowable expense — the refund is made of expenses. Mileage or van costs, tools, protective clothing, insurance, phone. (Full list in our expenses A–Z.)
  3. File early. The refund can be claimed from 6 April. Subbies who file in April–May get their money in weeks; subbies who file in January wait with everyone else. Same return, eight months' difference in cashflow.

Watch-outs

  • 30% deductions mean you're not registered (or not matched) under CIS — fix that with HMRC today; it's an instant 10-point pay rise.
  • Materials you genuinely supplied shouldn't have CIS deducted from them — check your statements.
  • Refund farms charging 20–30% of your refund for a standard return: you're giving away hundreds for something a proper accountant does as part of a monthly package.

CIS returns are core work for us: deduction statements tracked in FreeAgent through the year, expenses captured properly, return filed in April, refund chased. It's built into our packages from £19 + VAT a month — usually a fraction of the refund it recovers.