(a) Where a person (in this subsection referred to as "the first-mentioned person") is assessed to tax under section 643 and that assessment to tax arises in consequence of and in respect of consideration receivable by another person (in this subsection referred to as "the second-mentioned person") -
(i) the first-mentioned person shall be entitled to recover from the second-mentioned person any part of that tax which the first-mentioned person has paid,
(ii) if any part of that tax remains unpaid at the expiration of 6 months from the date when it became due and payable, it shall be recoverable from the second-mentioned person as though the second-mentioned person were the person so assessed, but without prejudice to the right to recover the tax from the first-mentioned person, and
(iii) for the purposes of subparagraph (i), the inspector shall on request furnish a certificate specifying the amount of income in respect of which tax has been paid and the amount of tax so paid, and
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