Corporation Tax Calculator

The main corporation tax rate for the 2026/27 tax year is set at 25% for companies with profits exceeding £250,000. This rate applies to the entire taxable profit once the upper limit is crossed. Companies with profits below £50,000 will continue to pay the small profits rate of 19%.

Marginal relief applies to companies with profits between £50,000 and £250,000 to smooth the transition between the 19% and 25% rates. The effective tax rate gradually increases from 19% to 25% as profits rise within this band. This prevents a cliff-edge tax increase at the £50,000 threshold.

The £250,000 upper limit and £50,000 lower limit are divided by the number of associated companies plus one. For example, if a company has two associated companies, the limits are effectively reduced to £83,333 and £166,667 respectively. This ensures that groups of companies do not artificially split profits to access lower rates.

Companies with profits exceeding £1.5 million must pay their corporation tax in nine monthly instalments. The first instalment is due six months and one day after the start of the accounting period. Subsequent instalments are due every three months until the tax bill is settled.

The corporation tax return must be filed with HMRC within 12 months after the end of the accounting period. However, the actual tax payment is due nine months and one day after the end of the accounting period for most companies. Failure to file on time results in automatic penalties regardless of whether tax is paid.