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Free tool

Free CIS calculator for UK subcontractors.

Enter your labour, materials and CIS status. See exactly what the contractor will deduct, what HMRC gets, and what lands in your bank. No signup, no email, no tracking. Free.

Invoice values

Labour and materials, ex-VAT

Enter the ex-VAT figures from your invoice. The CIS deduction only ever applies to the labour element.

£
£

Only the genuine pass-through cost — any markup counts as labour.

CIS status

Your registration with HMRC

Subcontractors registered with the CIS scheme get 20% deducted. Not registered = 30%. Gross payment status = 0% (rare).

VAT

Are you VAT registered?

Worked example: a typical heating engineer invoice

Sam fits a new combi boiler for a main contractor on a new build. Labour £1,200, materials £350, ex-VAT. Sam is CIS-registered.

  • CIS deduction = 20% of £1,200 = £240
  • Gross invoice = £1,200 + £350 = £1,550
  • Sam receives = £1,550 − £240 = £1,310
  • HMRC receives = £240(counts toward Sam's self-assessment bill at year-end)

If Sam wasn't registered, the contractor would deduct 30% of labour — £360 — instead of £240. Worth registering on day one.

Background

What is CIS?

The Construction Industry Scheme is HMRC's way of collecting tax up front from construction subcontractors. When a main contractor pays a sub, the contractor deducts a percentage and sends it straight to HMRC as advance tax on the sub's behalf. The sub gets the rest as their net pay.

CIS only ever bites on the labour element of the work, not the materials. The thinking: HMRC wants advance tax on profit, and materials at cost aren't profit — they're a pass-through. Anything you mark up on materials, though, counts as labour and gets deducted.

Three rates, depending on the sub's status with HMRC: 0% for the rare few who hold gross payment status, 20% for the standard CIS-registered sub, and 30% as a penalty rate for unregistered subs. Registering with HMRC is free and drops you from 30% to 20% immediately.

At the end of the tax year you complete a self-assessment. You subtract your real business expenses, work out your actual tax owed, and reclaim the difference against what was already deducted under CIS. Most subbies see a rebate.

What does the deduction actually apply to?

LabourDeducted

The full ex-VAT labour figure.

Materials at costNot deducted

Genuine pass-through cost only — bills, receipts, no markup.

Markup on materialsDeducted

Anything you add above the cost is treated as labour and deducted.

VATNot deducted

VAT sits on top of the gross invoice. Handled through your VAT return, not CIS.

Plant hire, fuel, travelDepends

Case-by-case. The official guidance is on gov.uk. gov.uk: what counts as materials →

How to register with HMRC

Registering for CIS as a subcontractor is free and takes about ten minutes online. You need a UTR (Unique Taxpayer Reference) from self-assessment first. Once you're on the system, the contractor verifies you via HMRC's lookup and drops your deduction rate from 30% to 20%.

Register for CIS on gov.uk →

There's also gross payment status — you get paid 100% with no deduction, then settle the full tax bill at year-end. You need to be turning over at least £30,000 a year(or £30k per partner / director) and pass HMRC's compliance checks. Rare for small subbies but worth knowing the option exists.

FAQ

Common CIS questions

Do I have to pay CIS if I'm not registered?
Yes — and at the higher 30% rate. CIS isn't an opt-in scheme: any subcontractor doing construction work for a contractor in the UK gets deducted. Registering with HMRC drops your rate from 30% to 20%, so it's worth doing on day one.
Can I claim CIS back?
Usually yes. The deductions are advance payments against your eventual income tax and Class 4 NI bill. At the end of the tax year you complete a self-assessment, subtract your business expenses, work out your real tax owed, then reclaim the difference. Most subbies get a rebate.
Does CIS apply to limited companies?
Yes. If you trade through a limited company and do CIS-scope construction work, the contractor still deducts. The 20% / 30% deduction is offset against your company's PAYE / NIC bill via your monthly Employer Payment Summary (EPS).
Does CIS apply to domestic work for a homeowner?
No. CIS only applies when one business pays another business for construction work. Working directly for a homeowner on their own house is outside the scheme — no deduction, no paperwork.
How often do I need to file?
As a subcontractor, you don't file a CIS return — the contractor does that monthly on your behalf. You only deal with CIS at the end of the tax year when you file your self-assessment.
What's the difference between CIS and PAYE?
PAYE is for employees — tax and NI deducted from a wage by an employer. CIS is for self-employed subcontractors — a flat 20% (or 30%) of your labour deducted by a contractor and paid to HMRC as advance tax. CIS gives no holiday pay, sick pay or employment rights — it's still self-employment.
Does CIS apply to my VAT?
No. CIS is calculated on the ex-VAT labour figure. VAT is added on top of the gross invoice and is handled separately through your VAT return. From March 2021, B2B construction services also fall under the VAT domestic reverse charge — a different rule from CIS, but commonly confused with it.

No signup

No email, no account, no friction. Open it, use it, close it.

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Your figures never leave your device. Nothing sent to a server.

Free to use

Free for any UK subcontractor, contractor, accountant or curious civilian.

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This calculator is for guidance only and is not tax or legal advice. Always check your figures against your own records and HMRC's official guidance, or speak to a qualified accountant for your specific situation.