Corporation Tax Calculator

Corporation Tax is the tax companies pay on their taxable profit. The main rate is 25% on profits over £250,000, with a small-profits rate of 19% for profits under £50,000. For example, at a profit of £100,000 taxed at the main rate: tax = £25,000.

First the taxable profit is determined (total income and gains minus allowable expenses and reliefs), then the relevant rate is applied — 25% main rate, 19% small-profits rate, or the main rate reduced by marginal relief in between.

The small-profits rate is 19% and applies to companies with taxable profits of £50,000 or less. Above £250,000 the full 25% main rate applies, and between the two thresholds marginal relief applies.

For profits between £50,000 and £250,000, marginal relief gradually increases the effective rate from 19% up to 25%, so you do not jump straight to the full main rate. HMRC provides a marginal relief calculator to work out the exact figure.

Costs incurred wholly and exclusively for the business are usually allowable, such as staff, premises and stock. Some costs are disallowed (e.g. client entertaining), and capital allowances cover qualifying equipment.

Most companies must pay Corporation Tax within 9 months and 1 day after the end of their accounting period, and file a Company Tax Return (CT600) with HMRC within 12 months. Large companies pay in quarterly instalments.

Yes. A trading loss can generally be carried forward and set against future profits, and in some cases carried back against earlier profits, within the limits and rules set by HMRC.

By claiming all allowable expenses and capital allowances, using reliefs such as R&D tax relief where eligible, and planning within the law. The tax is charged on taxable profit, so accurate accounts matter.