CIS Tax Refund Calculator
Estimate what HMRC owes you in under a minute. Built on 2025/26 rules by accountants who file these claims every day.
How much does HMRC owe you?
CIS contractors deduct a flat 20% — most subcontractors overpay all year. Check in 60 seconds. No email needed.
Estimate uses 2025/26 rules: £12,570 personal allowance, 20%/40% bands, Class 4 NI at 6%/2%, CIS withholding at your rate, £1,000 trading allowance where it beats itemised expenses. Your exact number comes from your CIS statements.
Every payment a CIS subcontractor receives has 20% deducted at source — 30% if you are not registered under the scheme. That deduction is taken from the gross invoice, before your £12,570 personal allowance and before a single expense is counted. It is a blunt instrument by design: HMRC collects first and sorts out the truth at year end, through your Self Assessment return.
The result is predictable. Most subcontractors finish the tax year having paid more than they owed, and the difference comes back only when someone files the return that proves it. The calculator above estimates that difference using the current bands, Class 4 National Insurance at 6% and 2%, and either your itemised expenses or the £1,000 trading allowance — whichever leaves you better off.
What the calculator takes into account
- Gross CIS income before deductions, and whether you are on the 20% or 30% rate.
- The £12,570 personal allowance, which the CIS deduction ignores entirely.
- Income tax at 20% and 40% across the relevant bands.
- Class 4 National Insurance at 6% between £12,570 and £50,270, then 2% above.
- Allowable expenses — van and mileage, tools, protective clothing, phone, use of home — or the trading allowance if that is worth more.
What it cannot know
An estimate is only as good as the numbers you put in. Contractors sometimes deduct at the wrong rate, statements go missing, and expenses get forgotten — all of which move the real figure. When we prepare the claim we reconstruct the year from actual CIS statements (or from bank records when statements were never issued), which is where most estimates turn out to be conservative.
When to claim
The tax year ends on 5 April, and returns can be filed from 6 April. Claims filed in April and May are usually repaid within a few weeks; the same claim filed in January sits in a queue behind eleven million other returns. Filing early is worth real money in waiting time, and it costs nothing extra.
CIS refund questions
Is this calculator free?
Yes, and it asks for no email address. You get the number on screen; whether you do anything with it is your choice.
How accurate is the estimate?
It applies current rates correctly to the figures you enter, so it is as accurate as those figures. The final number comes from your actual CIS statements, which is why the claim we prepare often exceeds the estimate.
I do not have my CIS statements. Can I still claim?
Yes. We reconstruct deductions from bank records and payment history, and can request data from HMRC where needed. Missing paperwork is one of the most common situations we deal with.
How long does the refund take?
Typically a few weeks for returns filed early in the tax year. Later in the year HMRC volumes rise and processing slows.
Can I claim for previous years?
Generally up to four tax years back. Many first-time clients recover several years at once.
I am being deducted 30%. Why?
That is the rate for subcontractors not registered with HMRC under CIS. We register you so future deductions drop to 20%, and the excess already taken comes back through your return.