Donaldson R F UK Corporation Tax Calculator
Work out Corporation Tax on company profits, including marginal relief between the small profits and main rate limits.
An estimate, not tax advice. Assumes augmented profits equal taxable profits (no dividend income from non-group companies), the common case. No change to these rates was found for 2026; checked on GOV.UK 7 October 2026.
How it's worked out
Profits up to £50,000 are taxed at the 19% small profits rate, and profits over £250,000 at the 25% main rate. In between, marginal relief tapers the effective rate smoothly from 19% to 25%, using the formula (upper limit − profits) × 3/200. Both limits are divided by the number of associated companies plus one — for example, 3 associated companies divide the limits by 4.
Source: GOV.UK: Corporation Tax rates and allowances, Corporation Tax marginal relief. Checked 7 October 2026.