“(1) If an officer of Revenue and Customs … discover[s], as regards any person (the taxpayer) and a year of assessment— (a) that any income which ought to have been assessed to income tax … have not been assessed, or … the officer … may … make an assessment in the amount … which ought in his or their opinion to be charged in order to make good to the Crown the loss of tax. …”
“(1) Subject to the following provisions of this Act … an assessment to income tax … may be made at any time not more than 4 years after the end of the year of assessment to which it relates (2) An objection to the making of any assessment on the ground that the time limit for making it has expired shall only be made on an appeal against the assessment.”
“(1) An assessment on a person in a case involving a loss of income tax … brought about carelessly by the person may be made at any time not more than 6 years after the end of the year of assessment to which it relates (subject to subsection (1A) and any other provision of the Taxes Acts allowing a longer period). (1A) An assessment on a person in a case involving a loss of income tax or capital gains tax‑‑ (a) brought about deliberately by the person, (b) attributable to a failure by the person to comply with an obligation under section 7,… … may be made at any time not more than 20 years after the end of the year of assessment to which it relates …”
“Section 36(1A)(b) … of TMA 1970 (fraudulent and negligent conduct) shall not apply where the year of assessment is 2008‑09 or earlier, except where the assessment on the person (“P”) is for the purposes of making good to the Crown a loss of tax attributable to P’s negligent conduct ….”