Calculate the standard marginal-relief position for a UK company in one Corporation Tax financial year.
Enter taxable total profits, qualifying exempt distributions, other associated companies and the actual Corporation Tax accounting-period dates. Unsupported periods and specialist cases require review.
Calculate standard UK Corporation Tax marginal relief using accounting-period dates, taxable total profits, qualifying distributions and other associated companies.
Augmented profits (A) are taxable total profits (N) plus qualifying exempt distributions that are not excluded. A selects the band; N is the taxable base. In the middle band, relief is 3/200 × (adjusted upper limit − A) × (N / A), deducted from tax at the 25% main rate.
The lower and upper limits are reduced for the exact number of days in the accounting period and divided by one plus the count of other associated companies. The result shows those adjusted limits, tax before relief, relief, final tax and effective rate.
Rule summary
The annual limits are £50,000 and £250,000 before short-period and associated-company adjustments. At or below the lower limit, the standard small-profits rate is 19%; at or above the upper limit, the main rate is 25%.
Only a Corporation Tax accounting period wholly within one financial year is supported here. Periods crossing 1 April may require financial-year apportionment; the calculator stops rather than guessing.
| Band selected by augmented profits | Standard tax treatment |
|---|---|
| At or below adjusted lower limit | 19% of taxable total profits |
| Above lower and below upper | 25% of taxable total profits, less 3/200 × (U − A) × (N / A) |
| At or above adjusted upper limit | 25% of taxable total profits |
Worked examples
For a full-year standard case with £90,000 taxable total profits and £8,000 qualifying exempt distributions, augmented profits are £98,000; there are no other associated companies.
Tax at 25% is £22,500. Relief is 3/200 × (£250,000 − £98,000) × (£90,000 / £98,000) = £2,093.88. Resulting tax is £20,406.12 (HMRC's published example rounds to whole pounds).
For a full-year standard case with £50,000 taxable total profits, no qualifying distributions and one other associated company, the limits divide by two to £25,000 and £125,000.
Tax at 25% is £12,500. Relief is 3/200 × (£125,000 − £50,000) = £1,125. Resulting tax is £11,375.
Verify the taxable total profits and classify any exempt distributions under CTA 2010 s18L before using the result.
Check associated-company control and exclusions, including companies associated for only part of the accounting period.
Keep liability calculation separate from the Corporation Tax payment deadline and final CT600 filing computation.
Read the guide
Read the supported rule, assumptions and worked examples behind this tool.
Assumptions and limits
This tool gives a practical estimate and depends on the assumptions shown below.
Reviewed on . Preserved source review from the accepted scoped statutory repair; this contract migration does not re-date that review.
Applies to: Non-ring-fence financial years 2023 through 2026; period and associated-company threshold adjustments.
Reviewed scope: Standard UK-resident company, not a close investment-holding company; supplied taxable/augmented profits, dates and associations; specialist regimes excluded.
Reviewed model: marginal-relief-calculator: non-ring-fence-fy2023-to-fy2026-reviewed-25 September 2026