Free Corporation Tax Calculator

Frequently Asked Questions

How is corporation tax calculated in the UK?

Corporation tax is calculated on your company's taxable profits for each accounting period. Since April 2023, the rate depends on your profit level: 19% for profits up to £50,000 (small profits rate), 25% for profits over £250,000 (main rate), and a marginal relief rate between £50,000 and £250,000.

What is the corporation tax rate for 2025/26?

For the financial year starting 1 April 2025, the main rate of corporation tax is 25% and the small profits rate is 19%. Marginal relief applies for profits between £50,000 and £250,000.

What is marginal relief and how does it work?

Marginal relief provides a gradual increase in the effective tax rate for companies with profits between £50,000 and £250,000. The relief is calculated using the formula: 3/200 × (Upper Limit − Augmented Profits) × (Taxable Profits / Augmented Profits). This ensures companies just above the £50,000 threshold don't face a sudden jump to the 25% rate.

What are associated companies and how do they affect my tax?

Associated companies are companies under common control. The marginal relief thresholds (£50,000 and £250,000) are divided equally between all associated companies plus yours. For example, with 1 associated company, the thresholds become £25,000 and £125,000.

What happens if my accounting period spans two financial years?

If your accounting period straddles 1 April (the start of a new financial year), your profits are split between the two financial years based on the number of days in each. The tax for each portion is calculated separately using the rates and thresholds for that financial year.

What is the small profits rate?

The small profits rate is 19%, available to companies with taxable profits of £50,000 or less (before dividing by associated companies). This rate was reintroduced from 1 April 2023. Before that date, all companies paid a flat 19% regardless of profit level.

When is corporation tax due?

Corporation tax is normally due 9 months and 1 day after the end of your accounting period. For example, if your year ends on 31 March 2025, payment is due by 1 January 2026. Large companies (profits over £1.5m) must pay in quarterly instalments.

How do I file my CT600 return?

You can file your CT600 corporation tax return online with HMRC. Taxpipe makes it simple — enter your company details, answer straightforward questions, and we calculate and file your CT600 for just £59. No accountancy jargon, no complex forms.