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HMRC internal manual

Company Taxation Manual

Corporation Tax self-assessment (CTSA): Assessments: Discovery - general


Under CTSA most assessments are self-assessments.

However, you can make ‘discovery’ assessments in certain circumstances. Subject to restrictions in FA98/SCH18/PARA43 - 45 you can make a ‘discovery assessment’ under Paragraph 41 (1) to make good to the Crown a loss of tax on discovering that:

  • an amount which ought to have been assessed to tax has not been assessed or
  • an assessment to tax is, or has become insufficient or
  • relief given is, or has become excessive.

A discovery assessment is only appropriate when a ‘discovery’ leads to additional tax liability on the company for that accounting period.