UK corporation tax changed significantly from April 2023. The rate is no longer flat — profits up to £50,000 pay 19% (small profits rate), profits above £250,000 pay 25% (main rate), and profits in between attract Marginal Relief that gradually increases the effective rate from 19% to 25%. This corporation tax calculator applies 2025/26 rates, handles Marginal Relief automatically, and allows you to account for associated companies — which reduce the thresholds proportionally.
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Associated companies reduce the thresholds. 0 = standalone company. Each associated company divides the limits by (1 + n).
Enter your company's taxable profit to calculate corporation tax
2025/26 rates. England, Scotland, Wales, Northern Ireland — corporation tax is UK-wide. Taxable profit may differ from accounting profit after allowances, reliefs, and adjustments. Consult your accountant.
Frequently Asked Questions
What are the UK corporation tax rates for 2025/26?
For the year to 31 March 2026, the small profits rate is 19% on profits up to £50,000. The main rate is 25% on profits above £250,000. Profits between £50,000 and £250,000 attract Marginal Relief, which produces an effective rate between 19% and 25% depending on the exact profit level.
What is Marginal Relief?
Marginal Relief reduces the corporation tax liability for companies with profits between the small profits limit (£50,000) and the main rate threshold (£250,000). The relief is calculated as: (£250,000 minus the profit) multiplied by (profit divided by £250,000) multiplied by 3/200. HMRC provides an online Marginal Relief calculator as well.
How do associated companies affect corporation tax?
If your company has associated companies (broadly, companies under common control), the £50,000 and £250,000 thresholds are divided equally between all companies. For example, with one associated company, the thresholds become £25,000 and £125,000. This can push companies into the main rate or Marginal Relief band unexpectedly.
What counts as taxable profit for corporation tax?
Taxable profit is your accounting profit adjusted for HMRC rules — adding back disallowable expenses (such as client entertainment), deducting capital allowances (instead of depreciation), and applying any loss relief or research and development credits. Your taxable profit may therefore differ significantly from your profit and loss account figure.
When is corporation tax due?
For small companies (profits under £1.5 million), corporation tax is due nine months and one day after the end of your accounting period. For large companies, quarterly instalment payments apply. The tax return (CT600) must be filed within 12 months of the accounting period end.
