Here we go ...
Notice of liability to income tax and capital gains tax
7(1) Every person who-
(a) is chargeable to income tax or capital gains tax for any year of assessment, and
(b) has not received a notice under section 8 of this Act requiring a return for that year of his
total income and chargeable gains,
shall, subject to subsection (3) below, within six months from the end of that year, give notice to an
officer of the Board that he is so chargeable.
7(2) In the case of persons who are chargeable as mentioned in subsection (1) above as the
relevant trustees of a settlement, that subsection shall have effect as if the reference to a notice
under section 8 of this Act were a reference to a notice under section 8A of this Act.
7(3) A person shall not be required to give notice under subsection (1) above in respect of a year
of assessment if for that year his total income consists of income from sources falling within
subsections (4) to (7) below and he has no chargeable gains.
7(4) A source of income falls within this subsection in relation to a year of assessment if-
(a) all payments of, or on account of, income from it during that year, and
(b) all income from it for that year which does not consist of payments,
have or has been taken into account in the making of deductions or repayments of tax under PAYE
regulations.
http://www.generalcommissioners.gov.uk/Documents/RulesLegislation/TMA1970ConsolidatedJan08.pdf