Corporation Tax Calculator
Work out UK Corporation Tax at 19% or 25% with marginal relief, adjusted for associated companies and short accounting periods, with the working shown.
Reviewed by Dany, RightSums team · Updated
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finance · Business · UK
Enter your company's taxable profits for the accounting period. The calculator applies the small profits rate of 19% up to £50,000, the main rate of 25% at £250,000 or more, and marginal relief in between using HMRC's 3/200 fraction. If your company has associated companies, the limits are divided between them, and if the accounting period is shorter than a year, they are cut in proportion to the days in the period. You see the tax due, your effective rate, the rate on your next pound of profit and each line of the marginal relief working, so you can check it against your return.
Accepted inputs
- Taxable profits
- Dividends from other companies
- Number of associated companies
- Accounting period length in days
Outputs
- Corporation Tax due
- Effective tax rate
- Marginal tax rate
- Profit after tax
- Lower and upper limits
- Marginal relief working
How to use the Corporation Tax Calculator
- Enter your company's taxable profits for the accounting period, after expenses and capital allowances.
- Add any dividends received from companies outside your group, as these count towards the limits even though they are not taxed.
- Enter the number of associated companies and the length of the accounting period in days.
- Read the tax due, the effective and marginal rates, and the table showing how the limits and marginal relief were worked out.
Frequently asked questions
How much Corporation Tax will I pay on £100,000 profit?
With no associated companies and a 12-month period, £100,000 falls in the marginal relief band. Tax at 25% is £25,000, less marginal relief of 3/200 × (£250,000 − £100,000) = £2,250, so you pay £22,750. That is an effective rate of 22.75%.
How is marginal relief calculated?
Marginal relief is 3/200 × (upper limit − augmented profits) × taxable profits ÷ augmented profits, taken off tax at 25%. It applies when profits are between £50,000 and £250,000. It means each extra pound of profit in that band is taxed at 26.5%, while the overall rate rises gradually from 19% to 25%.
How do associated companies affect Corporation Tax?
The £50,000 and £250,000 limits are divided by one plus the number of associated companies. With 3 associated companies the limits become £12,500 and £62,500, so £40,000 of profit pays £10,000 less £337.50 marginal relief, which is £9,662.50 rather than the £7,600 it would pay on its own.
What if my accounting period is shorter than 12 months?
The limits are reduced in proportion to the length of the period, counted in days. For a 182-day period, the upper limit is £250,000 × 182 ÷ 365 = £124,657.53. Profits of £60,000 in that period pay £15,000 less £969.86 marginal relief, which is £14,030.14.
What is the Corporation Tax rate for 2026?
For accounting periods from 1 April 2023, the main rate is 25% for profits over £250,000 and the small profits rate is 19% for profits of £50,000 or less, with marginal relief between the two. These rates and limits are unchanged for the 2026 financial year.
Sources
The rates and rules in this tool come from:
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