Corporation Tax rises with profit levels. Marginal relief bridges the gap, easing businesses from the 19% small profits rate to the 25% main rate.
The Corporation Tax Main Rate applies to companies with profits exceeding £250,000 and is currently set at 25%. For companies with profits up to £50,000, a Small Profit Rate (SPR) of 19% is applicable.
For profits between £50,000 and £250,000, a marginal rate of Corporation Tax is used to smooth the transition between the lower and upper limits. The lower and upper thresholds are also adjusted proportionately for short accounting periods of less than 12 months and for companies with associated entities.
Marginal relief gradually increases the effective Corporation Tax rate from 19% at profits of £50,000 to 25% at profits over £250,000. To calculate the Corporation Tax due, you multiply your profits by the main rate of 25% and subtract the marginal relief. For the current 2025 fiscal year, the marginal relief fraction is 3/200.