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HMRC internal manual

Company Taxation Manual

Corporation Tax self-assessment (CTSA): Assessments : Time limit


Unless the provisions of the Taxes Acts allow a longer period, the time limit for making a discovery assessment is four years after the end of the accounting period.

The time limit is extended to six years where the discovery assessment is made to recover loss of tax brought about by the carelessness of the company or a related person, and 20 years where the loss of tax is:

  • brought about deliberately by the company or a related person, or
  • attributable to a failure by the company to notify chargeability under Paragraph 2, Sch18 of FA98, or
  • attributable to an avoidance scheme where the company has not provided the information required by Section 309,310 or 313 of FA04.

A related person means:

  • a person acting on behalf of the company, or
  • a person who was a partner of the company at the relevant time.

For assessments made before 1 April 2010, subject to transitional provisions at SI2009/403 art 8, the time limit was six years in all cases unless the loss of tax was attributable to fraudulent or negligent conduct, when the 21 year time limit applied.

A company can object to an assessment on the grounds that the time limit for making it has expired only by making an appeal against the assessment.