INTM255770 | Controlled Foreign Companies: Computation of Chargeable Profits and Creditable Tax: Time limit
From HM Revenue & Customs · International Manual
The claim must be made within 20 months following the end of the starting period or such longer period as the Commissioners of HM Revenue & Customs may allow, by the United Kingdom company or companies having a majority interest (determined in accordance with INTM255720) in the company for the starting period.