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HMRC internal manual

COTAX Manual

HM Revenue & Customs
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Assessing: CTSA assessments: time limit for self assessment

A company can make a self assessment up to 4 years from the end of the AP to which it refers.

In practice, a revenue determination is usually made 18 months after the end of the company’s AP. In that case, the company can deliver a return and self assessment up to three years after the time the determination could first have been made or 12 months from the actual date of the determination, if that is later.


  • COM23170 for more information
  • COM23013 for legislation applying to this subject.