Corporation Tax calculator with marginal relief
Profit after allowable expenses and capital allowances, before Corporation Tax.
The profit limits are divided by the number of associated companies plus one. Standard 12-month year assumed.
- BandMarginal relief applies
- Lower limit£50,000
- Upper limit£250,000
- Effective rate23.4%
- Profit after tax£91,950
Corporation Tax due
£28,050
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How does the corporation tax calculator work?
UK Corporation Tax is 19% on profits up to £50,000 and 25% on profits above £250,000. Between those limits marginal relief applies, so the effective rate rises gradually from 19% to 25%. The limits are divided by one plus the number of associated companies.
How it works
Two rates and a sliding scale
Companies with profits up to £50,000 pay the small profits rate of 19%. Above £250,000 the main rate of 25% applies to all profits. In between, the tax is calculated at 25% and reduced by marginal relief of 3/200 of the amount by which profits fall short of £250,000.
Associated companies
If you control other companies, or are controlled alongside them, the £50,000 and £250,000 limits are divided between the group. Two associated companies, for example, each have limits of £25,000 and £125,000.
Short or long periods
The limits are reduced for accounting periods shorter than 12 months. This calculator assumes a standard 12-month year.
Rates used, 2026/27
- Small profits rate19% up to £50,000
- Main rate25% above £250,000
- Marginal relief3/200 of the shortfall
- Effective rate at £150,00024%
Last checked November 2026 against GOV.UK: Corporation Tax rates and allowances. General information, not tax advice.
A worked example
A company with £150,000 profit pays £36,000, an effective rate of 24%, because marginal relief of £1,500 reduces the £37,500 main-rate bill.
Questions about this calculator
When is Corporation Tax due?
Normally 9 months and 1 day after the end of the accounting period. The Corporation Tax return itself is due 12 months after the period ends.
What counts as profit?
Taxable profit is accounting profit adjusted for items such as depreciation and entertaining, with capital allowances added in. Good bookkeeping makes that calculation faster and cheaper.
Do large companies pay differently?
Companies with profits over £1.5 million, divided among associated companies, pay tax in quarterly instalments instead of one payment.
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