UK Corporation Tax Calculator

There are two rates and a sliding scale between them. Companies with taxable profits up to £50,000 pay the small profits rate of 19%. Companies with profits of £250,000 or more pay the main rate of 25%. Between £50,000 and £250,000 you pay the 25% main rate reduced by marginal relief, which produces an effective marginal rate of 26.5% on the profit in that band.

Marginal relief tapers the jump from 19% to 25%. The formula is: Corporation Tax = (profits × 25%) − (£250,000 − profits) × 3/200, where 3/200 is the standard marginal relief fraction. In effect, the first £50,000 is taxed at 19% and the slice from £50,000 to £250,000 is taxed at 26.5%, so a company on £100,000 pays an effective rate of about 22.75%.

Because marginal relief only tapers within the £50,000–£250,000 band, the government recoups the benefit of the 19% starting rate as your profits climb. That clawback makes each extra £1 of profit in the band cost 26.5p — higher than the headline 25% main rate. It's the corporate mirror of the personal £100k trap: an intermediate band with a marginal rate above the top rate.

If you control other companies (broadly, companies under common control), the £50,000 and £250,000 thresholds are divided by the total number of associated companies plus one. Two associated companies each get a £25,000 lower limit and £125,000 upper limit, so profits hit the 25% rate far sooner. Add any associated companies below to see the effect on your thresholds and bill.

For most small companies, Corporation Tax is due nine months and one day after the end of your accounting period — for example, a year ending 31 March 2025 means payment by 1 January 2026. The return (CT600) must be filed within 12 months of the period end. Large companies (profits over £1.5m) pay in quarterly instalments. This calculator estimates the annual charge, not the payment schedule.

Legitimately: pay a director's salary and employer pension contributions (both deductible), claim capital allowances including the Annual Investment Allowance and full expensing on qualifying equipment, deduct genuine business costs, and use R&D reliefs if you qualify. For owner-managers, the salary-versus-dividend split also affects the total tax across the company and your personal return — model it with our salary vs dividend calculator.