ToolsCorporation Tax estimator
Corporation Tax estimator
Enter your taxable profit to estimate your Corporation Tax bill, including the small profits rate, main rate and marginal relief.
Taxable profit is your profit after allowable expenses and tax adjustments. Associated companies reduce the £50,000 and £250,000 thresholds proportionally.
An estimate for the financial year beginning 1 April 2026, assuming a 12-month accounting period and that your augmented profits equal your taxable profits (no exempt distributions from other companies). Ring-fenced (oil and gas) profits, close investment holding companies and non-standard periods are treated differently. Your exact figure is worked out when you file. General guidance, not tax advice.
Common questions
How is Corporation Tax calculated?
Profits up to £50,000 are taxed at the 19% small profits rate and profits of £250,000 or more at the 25% main rate. Profits in between are taxed at 25% with marginal relief, giving an effective rate between 19% and 25%.
What is marginal relief?
Marginal relief gradually reduces your Corporation Tax when profits fall between £50,000 and £250,000, so you are not pushed straight to the full 25%. The effective marginal rate on profits in that band is 26.5%.
What are associated companies?
If your company is under common control with other companies, they count as associated and the £50,000 and £250,000 thresholds are divided between them. One associated company, for example, halves both thresholds.
Is this the exact amount I will pay?
It is an estimate. Your actual bill depends on capital allowances, losses, reliefs and other adjustments to your taxable profit. OneFiler works out the precise figure when you prepare your CT600.