About the CISTaxCalc CIS calculator
CISTaxCalc.co.uk is a free CIS tax calculator for UK construction subcontractors: bricklayers, sparks, plumbers, joiners, scaffolders and everyone else paid after a CIS deduction.
Why it exists
Most tax calculators are built for employees on PAYE. Subcontractors get paid differently: a contractor takes 20% or 30% off the labour on every invoice, you pay for your own materials, van and tools, and the real tax position only becomes clear when you file Self Assessment months later. We wanted a tool that shows, in seconds and on a phone, what you will actually take home, what to set aside, and whether HMRC is likely to owe you a refund.
How we keep it accurate
All figures follow HMRC's published CIS rules and the 2026/27 Income Tax and Class 4 National Insurance thresholds. Rates sit in one place in the code, so when HMRC changes a threshold we update it once and every page follows. The calculator runs in your browser. The numbers you type are not stored on our servers.
What it is not
This is an estimating tool, not financial advice. Your own position depends on things a calculator cannot see, such as other income, pension contributions or past losses. Always check important decisions with a qualified accountant.
Start with the CIS tax calculator, or get in touch if something looks wrong.