CTM98040 | Corporation Tax self-assessment (CTSA): capital allowances: time limit - when not extended
From HM Revenue & Customs · Company Taxation Manual
FA98/SCH18/PARA82 (3) - (4)
The extended time limits in Paragraph 82 (1) do not apply when the enquiry is restricted to a previous amendment of a return making, amending or withdrawing a claim for capital allowances (Paragraph 82 (4)).
An enquiry is restricted to such a previous amendment if:
the scope of the enquiry is limited because you issue the notice of enquiry after the time that you may open an enquiry into the whole of the return,
and
the amendment giving rise to the enquiry consisted of the making, amending or withdrawing of a capital allowances claim.