“(1) Where a person has failed to make any returns required under this Act (or under any provision repealed by this Act) or to keep any documents and afford the facilities necessary to verify such returns or where it appears to the Commissioners that such returns are incomplete or incorrect, they may assess the amount of VAT due from him to the best of their judgment and notify it to him. … (8) In any case where – (a) as a result of a person’s failure to make a return for a prescribed accounting period, the Commissioners have made an assessment under subsection (1) above for that period, (b) the VAT assessed has been paid but no proper return has been made for the period to which he assessment related, and (c) as a result of a failure to make a return for a later prescribed accounting period, being a failure by a person referred to in paragraph (a) above or a person acting in a representative capacity in relation to him, as mentioned in subsection (5) above, the Commissioners find it necessary to make another assessment under subsection (1) above, Then, if the Commissioners think fit, having regard to the failure referred to in paragraph (a) above, they may specify in the assessment referred to in paragraph (c) above an amount of Vat greater than that which they would otherwise have considered to be appropriate.”
“(1A) Where the Commissioners – (a) have assessed a person to VAT for a prescribed accounting period (whenever ended), and (b) in doing so, have brought into account as output tax an amount that was not output tax due, They shall be liable to credit the person with that amount.”
“The Commissioners shall not be liable on a claim under this section – (a) to credit an amount to a person under subsection (1) or (1A) above, or (b) [not applicable], if the claim is made more than 3 years after the relevant date.”