🏢 Corporation Tax Calculator

Small profits rate · Main rate · Marginal relief · 2026/27

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Affects profit thresholds if you have associated companies

Corporation Tax — 2026/27

Corporation Tax Due—
Effective Rate—
Rate Applied—
Profit After Tax—
Corporation tax is due 9 months and 1 day after your accounting period ends (for companies not paying by instalments).

Corporation Tax Rates 2026/27

UK corporation tax has two main rates depending on the level of taxable profits:

  • Small profits rate (19%) — applies to profits up to £50,000
  • Main rate (25%) — applies to profits over £250,000
  • Marginal relief — for profits between £50,000 and £250,000, a tapered rate between 19% and 25% applies

Marginal Relief Explained

Companies with profits between £50,000 and £250,000 receive marginal relief, which tapers the effective rate between 19% and 25%. The marginal relief formula reduces the main rate tax by a fraction of the difference between the upper and lower limits. This means a company with £150,000 profit pays an effective rate of approximately 22%.

💡 These thresholds are divided by the number of associated companies plus one. If you have one associated company, the thresholds become £25,000 and £125,000.

When is Corporation Tax Due?

For most companies, corporation tax is due 9 months and 1 day after the end of the accounting period. Large companies (profits over £1.5m) pay by quarterly instalments. The CT600 return must be filed within 12 months of the accounting period end.