Corporation tax is a tax levied on the profits earned by companies and organizations in the United Kingdom. It is levied on the taxable profits of limited companies and certain other organizations, including co-operatives, clubs, societies, and associations. The rate of corporation tax in the UK is currently 19%. Corporation tax is different from other taxes, such as income tax and VAT, in that it is levied on the profits of a company rather than on the income or sales of an individual. Companies are required to calculate their taxable profits for a given period (known as an accounting period), and pay corporation tax on those profits. The accounting period for corporation tax purposes is generally the same as the company's financial year.

In the UK, companies are required to file a corporation tax return and pay any corporation tax due within nine months and one day of the end of their accounting period. If a company is unable to pay its corporation tax on time, it may be able to arrange a payment plan with HM Revenue and Customs (HMRC), the UK's tax authority. There are a number of reliefs and allowances available to companies that are liable for corporation tax in the UK, which can help to reduce their tax liability. For example, companies may be able to claim relief for research and development expenses, or for investments in plant and machinery.