The normal time limit for making assessments to income tax and capital gains tax from 1 April 2010 is four years after the end of the year of assessment to which it relates. Before 1 April 2010 the time limit was five years after the 31 January following the year of assessment to which it related (TMA 1970, s. 34).
From 6 April 2015 an assessment to capital gains tax includes a determination in respect of non-resident capital gains tax disposals under TMA 1970, s. 29A (TMA 1970, s. 34(1A)).
For corporation tax, the time limit is four years following the end of the accounting period to which the assessment relates (FA 1998, Sch. 18, para. 46).