Corporation Tax
Calculator 2025/26

The main Corporation Tax rate for 2025/26 is 25% on profits above £250,000. The small profits rate is 19% on profits up to £50,000. Profits between £50,000 and £250,000 receive Marginal Relief, creating an effective taper between 19% and 25%. These rates have been in place since April 2023.

Marginal Relief tapers the effective CT rate for profits between £50,000 and £250,000. The relief is calculated using HMRC's formula: (upper limit − profits) × standard fraction × (profits ÷ augmented profits). The effect is a gradual increase in effective rate from 19% to 25% across the band.

The £50,000 and £250,000 thresholds are divided by the number of associated companies plus one. If you have one associated company, both thresholds halve — so the small profits rate applies only up to £25,000 and the main rate above £125,000. Associated companies include those under common control.

For most small and medium companies, Corporation Tax is due 9 months and 1 day after the end of your accounting period. Your CT600 return must be filed within 12 months. Large companies (profits over £1.5m) pay in quarterly instalments. HMRC charges interest on late payments.

Allowable expenses include salaries and employer NI, office and equipment costs, travel, marketing, professional fees, software subscriptions, interest on business loans, and capital allowances. Dividends paid to shareholders are not deductible — they come out of post-tax profits.