CIS Tax Rebate Calculator
Estimate whether your CIS deductions are likely to produce a Self Assessment refund or leave more tax to pay. This page is for self-employed subcontractors and partners who have CIS deducted during the year, then claim credit for those deductions against Income Tax and Class 4 National Insurance.
Estimate your year-end CIS refund
Enter your annual CIS income, expenses and deductions. For a single invoice deduction, use the CIS Tax Calculator instead.
Use the full invoice income before CIS deductions.
Use your monthly payment and deduction statements.
Employment, pension or other non-dividend income.
Optional adjusted-net-income style reduction for this estimate.
Manual amount if your tax return adds extra charges.
Limited company route is different
GOV.UK says limited company subcontractors generally claim CIS deductions through their monthly payroll scheme by sending EPS/FPS information. Any excess that cannot be set off may be refunded or set against Corporation Tax after the tax year, once the relevant returns are submitted.
Refund driver
Expenses
The more allowable costs you have, the lower your profit and the more likely CIS deducted at source exceeds the final bill.
Tax credit
CIS paid
CIS is not an extra tax. It is credited against your Self Assessment tax and National Insurance.
Watch point
POA
Payments on account can affect January cash flow even when the year-end balancing position looks manageable.
A CIS rebate is really a year-end tax balance
The word "rebate" is useful shorthand, but it can make CIS sound like a separate pot of money. It is not. GOV.UK explains that sole traders and partners still work out the correct tax and National Insurance for the business, then HMRC takes off the deductions contractors have already made.
That is why two subcontractors with the same CIS deducted can end up with different results. One may have high van, tools, insurance and accountancy costs, so taxable profit is lower and a refund is due. Another may have fewer expenses, PAYE income on the side, student loan repayments or payments on account, so there is still something to pay.
| Tax return item | How it affects the refund |
|---|---|
| Gross CIS income | Included as business turnover before deductions. |
| Allowable expenses | Reduce taxable profit. |
| CIS deducted | Credited against tax and NI. |
| Other income | Can use tax bands and reduce the refund. |
| Payments on account | Can change the Self Assessment statement balance. |
How this CIS rebate calculator works
Inputs used
- Tax year and Income Tax region.
- Gross CIS income, CIS tax deducted and allowable business expenses.
- Other taxable income, PAYE tax already deducted and payments on account already paid.
- Optional pension/Gift Aid adjustment and manual student loan or other Self Assessment charges.
Calculation method
- Calculate taxable business profit from CIS income minus either actual expenses or the GBP 1,000 trading allowance.
- Add other taxable income and apply the Personal Allowance taper where income exceeds GBP 100,000.
- Apply England/Wales/Northern Ireland or Scottish Income Tax bands to the estimated taxable income.
- Calculate Class 4 National Insurance on self-employed profit above the Lower Profits Limit.
- Compare Income Tax, Class 4 NI and manual charges with CIS deductions, PAYE tax deducted and payments on account already paid.
Assumptions
- The main estimate is for sole traders and individual partners, not limited companies.
- Other income is treated as non-savings, non-dividend income for band purposes.
- Class 4 National Insurance is included; voluntary Class 2 National Insurance is not charged automatically.
- Payments on account are shown as an indicative cash-flow warning only.
What this does not cover
- It does not check whether a payment should have been inside CIS. Use the CIS Tax Calculator for invoice deduction checks and GOV.UK CIS guidance for scope.
- It does not calculate limited company payroll set-off, Corporation Tax or end-of-year company repayment claims. Use GOV.UK limited-company CIS refund guidance if you trade through a company.
- It does not calculate capital allowances, basis-period transition, VAT, Making Tax Digital, student loan plan rules, Child Benefit Charge or benefit entitlement.
- It does not replace Self Assessment software, HMRC calculation, or professional advice where records are incomplete or multiple trades are involved.
Worked example: why a rebate appears
Imagine a subcontractor has GBP 45,000 of gross CIS income and contractors have deducted GBP 7,200 across the year. They also have GBP 9,000 of allowable expenses for tools, van costs, insurance, phone, accountancy and other business costs.
The taxable profit is GBP 36,000 before the Personal Allowance. On a simple England/Wales/Northern Ireland estimate with no other income, the Income Tax and Class 4 National Insurance bill is lower than the GBP 7,200 already withheld. That difference is the likely refund, before HMRC checks the return and any existing statement balance.
If the same person had PAYE work, fewer expenses or student loan deductions through Self Assessment, the refund would shrink. If they had made payments on account already, the statement could move further towards a refund.
Records to pull together before claiming
Keep every monthly payment and deduction statement from contractors. GOV.UK says contractors give these to help with accounting, and HMRC can ask for evidence if deductions do not match records.
Also keep invoices, receipts, mileage logs, finance agreements, insurance documents and bank records. The calculator lets you enter one total expense figure, but your return still needs a real basis for that total.
If you are claiming after the tax year has ended, the normal route is your Self Assessment tax return. If you are trying to claim during the current tax year, GOV.UK points individual subcontractors to form CIS40.
Practical refund checks before you file
Use gross income, not net bank receipts
For Self Assessment, record the full invoice income and the CIS deductions separately. Do not enter only the amount that landed in your bank.
Do not double count materials
If your contractor already excluded materials when deducting CIS, that does not stop you recording actual business costs correctly in your accounts.
Check side income
PAYE income, pensions and other taxable income can use up Personal Allowance or tax bands before your self-employed profit is taxed.
Separate company claims
Limited company CIS deductions are normally set off through payroll returns first. Do not treat them like an individual Self Assessment rebate.
CIS tax rebate FAQs
Why do CIS subcontractors often get refunds?
What expenses can I include?
When do I get a CIS refund?
What if I also have PAYE income?
Can a limited company use this rebate estimate?
Official sources
Last verified: May 9 2026. Calculations are estimates based on the published rules and assumptions shown on this page.
- GOV.UK CIS subcontractor: pay tax and claim back deductions - how sole traders, partners and limited companies claim or set off CIS deductions
- GOV.UK CIS subcontractor overview - 20% and 30% deduction overview and advance-payment treatment
- GOV.UK CIS 340 guide - detailed HMRC guidance for contractors and subcontractors, including deduction statements and repayment treatment
- GOV.UK Income Tax rates and allowances - Personal Allowance, England/Wales/Northern Ireland rates and allowance taper
- GOV.UK National Insurance rates and allowances - Class 4 National Insurance thresholds and rates for self-employed profits
- GOV.UK trading allowance - GBP 1,000 trading allowance rules and expense alternative
- GOV.UK Self Assessment payments on account - 31 January and 31 July payments on account rules
- Scottish Government Income Tax rates and bands - Scottish non-savings, non-dividend Income Tax rates for 2025/26 and 2026/27