Corporation tax and marginal relief calculator

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Enter a company's taxable profit to see the corporation tax due, the marginal relief and the effective rate. For financial year 2026 (1 April 2026 to 31 March 2027).

Taxable profit for the year (£) A 12-month accounting period, with no dividends received from non-group companies Associated companies Other companies under common control. Each one shrinks both thresholds.

General information, not advice. The result is an estimate for a simple case; a real computation depends on the full facts.

How the calculation works

Profit up to £50,000: Small profits rate: 19%.
Profit over £250,000: Main rate: 25%.
Profit between the two: Tax at 25%, less marginal relief of 3/200 × (upper limit − profit).
Associated companies: Both limits are divided by the number of associated companies plus one. With one associated company they become £25,000 and £125,000.

Why the effective rate is not the marginal rate

Inside the band, each extra pound of profit is taxed at 26.5%, because it both attracts the 25% main rate and reduces the relief. The effective rate, tax divided by profit, climbs gradually from 19% to 25%. A company with £100,000 of profit pays £22,750, an effective 22.75%. The full table is on the rates & thresholds page.

What this calculator leaves out

Short or long accounting periods: The limits are reduced in proportion for a period under 12 months.
Exempt distributions: Dividends from non-group companies are added to profit to test the limits, which reduces the relief.
Periods straddling 1 April: Each financial year is computed separately.

Source

GOV.UK: Marginal Relief for Corporation Tax. Rates on this site were verified on 13 August 2026.