SolvedSACM12200 | Overpayment relief: Error or mistake relief claims no longer possible
From HM Revenue & Customs · Self Assessment Claims Manual
Overpayment relief replaces the old error or mistake rules for individuals, partnerships and companies.
From 1 April 2010, it is not possible to make a claim for the old error or mistake relief for any period.
If, exceptionally, you need to refer to the old guidance for error or mistake relief see SACMApp1.