UK corporation tax calculator
Work out corporation tax at 19%, 25% or with marginal relief, and see when it's due to be paid and filed.
How it's calculated
For the financial year starting 1 April 2026, companies pay 19% on profits up to £50,000 and 25% on profits over £250,000. Between the two, you pay 25% less marginal relief.
Marginal relief = (upper limit − augmented profits) × (taxable profits ÷ augmented profits) × 3/200. Augmented profits are taxable profits plus exempt dividends from companies outside your group. Both limits are divided by the number of associated companies plus one, and shortened in proportion for periods under 12 months.
Worked example
A company with no associated companies makes taxable profits of £100,000 in a 12-month period. Tax at 25% is £25,000. Marginal relief is (£250,000 − £100,000) × 3/200 = £2,250. Corporation tax is £22,750, an effective rate of 22.75%.
When it's due
- Pay corporation tax 9 months and 1 day after the end of the accounting period
- File the CT600 return within 12 months of the end of the accounting period
- Companies with profits over £1.5 million (divided by associated companies plus one) usually pay in quarterly instalments instead
What this calculator doesn't cover
- Close investment-holding companies, which pay 25% on all profits
- Ring-fenced oil and gas profits
- Quarterly instalment schedules for large companies
- Reliefs not already included in your taxable profit figure, such as R&D relief
An estimate for planning, not tax advice. Rates and limits checked 27 October 2026 for the financial year starting 1 April 2026.
Common questions
What is an associated company?
Another company that your company controls, that controls yours, or that is under the same control, at any time in the accounting period. Companies that don't carry on a trade or business in the period are ignored.
Why is the rate in the marginal band higher than 25%?
Each extra pound of profit between £50,000 and £250,000 is taxed at an effective 26.5%, because the relief shrinks as profits rise. The overall rate on all your profit still stays between 19% and 25%.
Should I enter profit before or after capital allowances?
After. Enter your taxable profit: accounting profit adjusted for disallowable costs, capital allowances and other tax adjustments.
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