CIS Tax Rebate Calculator: Estimate Your CIS Refund
Use our free CIS tax rebate calculator to check how much tax you could get back from HMRC. Enter your income before CIS deductions, materials, other allowable business expenses and the tax your contractors deducted. You will see your estimated refund or any tax still to pay after Income Tax and National Insurance.
The calculator covers tax years 2022/23 to 2026/27 for sole traders and individual partners. It uses Income Tax rates for England, Wales and Northern Ireland, and your results update as you enter your figures.
An estimate to help you, not tax advice. It assumes your CIS work is your only income, and uses HMRC's rates for the year you pick, for England, Wales and Northern Ireland.
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How to Use Our CIS Tax Rebate Calculator
Here is how to use our CIS tax rebate calculator step by step.
Step 1: Select the Tax Year
Select the tax year your income and deductions relate to. The calculator has the 2025/26 tax year selected by default. This tax year ran from 6 April 2025 to 5 April 2026.
Choose an earlier year to check a previous period, or select 2026/27 to estimate your position for the current tax year. The dropdown highlights late years and relevant deadlines.
Step 2: Choose Sole Trader or Partner
Select Sole trader if you run your business individually. Choose Partner if you are an individual in a business partnership.
Partner mode changes the income and deduction fields to ask for the full partnership figures.
Step 3: Enter Your CIS Income Before Deductions
Enter your total CIS business income before contractors deducted tax. Include amounts paid for materials and exclude any VAT you charged.
For example, if you received £28,000 after £7,000 of CIS deductions, enter £35,000.
In Partner mode, enter the whole partnership’s CIS income. You will also need to enter your percentage share in Step 6.
Step 4: Enter Your CIS Deductions or Use the 20% Estimate
Add up the CIS deductions on your statements for the selected tax year. Enter the total your contractors deducted, including deductions at 30% or a mixture of rates.
If you need an estimate, click the Not sure? Estimate it at 20% button. Our cis tax refund calculator applies 20% to your income after subtracting materials. Other business expenses do not reduce this deduction estimate.
If you change your income or materials figure, click Not sure? Estimate it at 20% again to update the estimated CIS deduction.
Step 5: Add Your Materials and Other Business Expenses
Enter the cost of materials you bought for your jobs under Materials. Use Other business expenses for your remaining allowable costs, keeping materials out of this total to avoid counting them twice.
Allowable costs can include tools, protective clothing, business vehicle and travel expenses, insurance, accountancy fees and the business share of your phone bills. Include only the amount you can claim for tax and exclude VAT you can recover.
Step 6: Enter Your Partnership Share, If Applicable
In Partner mode, enter your percentage under Your share of the partnership. The calculator uses this percentage to calculate your share of both partnership profit and CIS deductions, then estimates your personal tax position.
Check that the earlier fields contain the full partnership totals. If you enter only your share in those fields, the calculator will reduce those figures again.
Step 7: View Your Results
Your results update automatically as you enter or change your figures in our cis tax refund calculator.
CIS Deducted
This shows the total CIS tax taken from your payments. In Partner mode, it shows your calculated share of the partnership’s deductions.
Estimated Refund or Tax Still to Pay
Check the middle card for your estimated refund or any remaining tax to pay.
A separate message appears when payments on account may be due. These are instalments towards the following year’s tax bill, payable in addition to the current year’s balance.
Tax and National Insurance Due
This shows your estimated annual Income Tax and National Insurance bill before crediting the CIS tax already deducted. Your CIS deductions may cover some or all of this amount.
Where Your CIS Goes
If you have an estimated refund, the chart and table show how much of your CIS deductions covers tax and National Insurance and how much could come back to you.
If you still owe tax, they show the part of your bill covered by CIS deductions and the balance remaining.
Your Detailed Calculation Breakdown
Click See how we worked it out to view your profit, allowances, Income Tax bands and National Insurance calculation. In Partner mode, the breakdown also shows your share of partnership profit.
How Is Your CIS Tax Refund Calculated?
Your CIS deductions count as advance payments towards your annual tax bill. Our calculator estimates the Income Tax and National Insurance due on your profit, then compares that amount with the tax your contractors deducted. HMRC settles the actual figures through your Self Assessment tax return.
Here is how our calculator takes your figures through each stage. The calculations below use 2025/26 figures for a sole trader with £40,000 of CIS income, £5,000 of materials, £3,000 of other business expenses and £7,000 of CIS deductions.
1: Calculate Your Profit After Materials and Business Expenses
The calculator first subtracts your materials and other allowable business expenses from your CIS income before deductions.
Profit = CIS income before deductions − materials − other business expenses
Using the figures above:
£40,000 − £5,000 − £3,000 = £32,000 profit
This leaves £32,000 before applying your Personal Allowance or calculating tax.
In Partner mode, the calculator also applies your partnership percentage to the partnership’s profit:
Your share of profit = Partnership profit × your percentage share ÷ 100
Your share then becomes the profit used for your personal tax calculation. Before calculating Income Tax, the calculator checks whether the trading allowance changes the amount it should deduct for costs.
2: Check Whether the £1,000 Trading Allowance Applies
In Sole trader mode, the calculator compares your total entered costs with the £1,000 trading allowance. When those costs are below £1,000, it uses the allowance instead, capped at the amount of your income.
For example, if you entered £40,000 of income and only £600 of total costs, the calculation using your actual costs would be:
£40,000 − £600 = £39,400 profit
The calculator would instead use the £1,000 allowance:
Profit using the trading allowance = CIS income − trading allowance
£40,000 − £1,000 = £39,000 profit
You cannot deduct both the trading allowance and your actual expenses.
Partnership income does not qualify, and other restrictions can prevent a sole trader from using the allowance, including income from an employer or a company they control.
The calculator assumes you qualify, so check the eligibility rules before claiming it.
In our main example, materials and other expenses total £8,000. The calculator therefore keeps the actual cost deduction and carries £32,000 profit into the next step.
3: Apply Your Personal Allowance and Calculate Income Tax
The calculator next deducts your available Personal Allowance from your profit. The standard allowance is £12,570.
Taxable income = Profit − available Personal Allowance
For our £32,000 profit:
£32,000 − £12,570 = £19,430 taxable income
Taxable income cannot fall below £0. For 2025/26 and 2026/27, the calculator applies these bands to the amount remaining after your available allowance:
Taxable income after the allowance
Income Tax rate
First £37,700
20%
£37,701 to £125,140
40%
Above £125,140
45%
Each rate applies only to the income within that band. All £19,430 in our example falls within the basic-rate band:
Income Tax = Taxable income × 20%
£19,430 × 20% = £3,886 Income Tax
If your profit exceeds £100,000, the calculator also reduces your Personal Allowance because it assumes CIS profit is your only income:
Allowance reduction = (Profit − £100,000) ÷ 2
For £112,000 profit, the reduction is £6,000, leaving a £6,570 allowance. The allowance reaches £0 at £125,140. The calculator uses the Income Tax bands for your selected year.
With Income Tax calculated, the next step adds National Insurance.
4: Calculate National Insurance for Your Selected Tax Year
The calculator uses your profit and the National Insurance rules for the year you selected. It calculates Class 4 and adds Class 2 where payable for earlier years.
Class 4 National Insurance on Your Profits
Class 4 uses your profit before deducting the Personal Allowance. The calculator applies the main rate to profit between the lower limit and £50,270, then applies the upper rate to profit above £50,270.
Tax year
Lower profit limit
Main rate up to £50,270
Rate above £50,270
2022/23
£11,908
9.73%
2.73%
2023/24
£12,570
9%
2%
2024/25 to 2026/27
£12,570
6%
2%
The 2022/23 figures reflect changes to rates and thresholds during that year.
The calculation combines the contributions from both profit bands:
Class 4 = (Profit within the main band × main rate) + (Profit above £50,270 × upper rate)
For our 2025/26 example, the profit within the main band is:
£32,000 − £12,570 = £19,430
The calculator then applies 6%:
£19,430 × 6% = £1,165.80 Class 4 National Insurance
The £32,000 profit does not reach the upper band, so that part of the calculation adds £0.
Class 2 National Insurance for Earlier Tax Years
For 2022/23 and 2023/24, the calculator also includes 52 weeks of Class 2 where payable:
Class 2 = Weekly rate × 52 weeks
For 2022/23:
£3.15 × 52 = £163.80
For 2023/24:
£3.45 × 52 = £179.40
These are full-year estimates. Compulsory Class 2 payments ended from 2024/25, so our 2025/26 example has a £0 Class 2 charge. The calculator excludes voluntary Class 2 contributions, which some people with low profits can choose to pay.
5: Compare Your CIS Deductions With Your Total Tax and National Insurance
The calculator now adds the Income Tax and National Insurance figures:
Total tax and National Insurance = Income Tax + Class 4 + Class 2
For our 2025/26 example:
£3,886 + £1,165.80 + £0 = £5,051.80
It then credits the CIS tax your contractors already deducted. In Partner mode, it first calculates your share of the partnership’s deductions:
Your CIS deductions = Partnership CIS deductions × your percentage share ÷ 100
For the sole trader example, the full £7,000 of CIS deductions counts against the £5,051.80 bill:
Estimated refund = CIS deductions − total tax and National Insurance
£7,000 − £5,051.80 = £1,948.20 estimated refund
If your deductions fall short of the bill, the calculator shows tax still to pay. For example, if contractors had deducted £2,000 against the same £5,051.80 liability:
Tax still to pay = Total tax and National Insurance − CIS deductions
£5,051.80 − £2,000 = £3,051.80 still to pay
Limitations of Our CIS Tax Rebate Calculator
Our CIS tax rebate calculator estimates your refund or tax still to pay from the figures you enter. The following limits explain what it leaves out and when you need a different calculation.
Income From Other Sources
The calculator assumes CIS work is your only income. It excludes PAYE employment income, rental income, dividends and other earnings. If you receive income from other sources, you need a calculation that includes your full tax position.
Scottish Income Tax Rates
The calculator uses Income Tax rates for England, Wales and Northern Ireland. It does not apply Scottish Income Tax bands, so Scottish taxpayers need a separate calculation.
Student Loans and Personal Tax Adjustments
The estimate excludes student loan repayments and adjustments for pension contributions, Gift Aid and Marriage Allowance. It also excludes other individual tax reliefs and charges that could change your final bill.
Expense Eligibility, Capital Allowances and Loss Relief
The calculator uses the expenses you enter without checking whether they qualify for tax relief. You need to check the eligibility of your costs before including them.
It does not calculate capital allowances or apply loss relief. If your total costs exceed your income, the calculator sets taxable profit to £0 without calculating any relief you could claim for the loss.
National Insurance Exceptions
The calculator does not adjust National Insurance for your age or any exemption that applies to you. For earlier tax years, it includes 52 weeks of Class 2 where payable and does not reduce that amount for part-year liability.
Previous Tax Payments and HMRC Balances
The displayed result does not account for payments on account you have already made. It also excludes penalties, interest and outstanding HMRC debts, so it does not show the final balance on your HMRC account.
The 20% Deduction Estimate
The Not sure? Estimate it at 20% button gives an approximation. It cannot account for every exclusion contractors apply when calculating CIS deductions.
Use the actual deductions on your CIS payment and deduction statements where available to give the calculator a more accurate starting figure.
Tax Return Filing and Refund Claims
This CIS tax return calculator does not submit your Self Assessment return or claim a refund. It also does not cover limited company CIS claims, which follow a different process.
Speak to our CIS accountants if you need help checking your figures, preparing your return or claiming a refund.
Yes, if your CIS deductions exceed your Income Tax and National Insurance bill. Sole traders and partners claim the difference through their Self Assessment tax return.
Does This CIS Tax Return Calculator Submit My Return?
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No. The calculator estimates your refund or tax still to pay. You need to submit your Self Assessment return separately, either yourself or through an accountant.
Rita writes practical accounting and tax guidance for business owners, drawing on her experience supporting businesses with accounts, tax and financial management.
