51.—(1) Subject to paragraph (2), where, in relation to the year ended 5th April 1993 or any subsequent year, an employer has not within 14 days after the end of a year paid to the collector the total net tax deductible by him in respect of all his employees during that year, the tax not so paid shall carry interest at the prescribed rate from the reckonable date until payment.
(2) Paragraph (1) shall not apply to any tax in respect of which a direction under regulation 42(2) or (3) has been made.
(3) In this regulation “the reckonable date”, in relation to any year, means the 14th day after the end of that year.
(4) A certificate of the collector that any amount of interest payable under this regulation has not been paid to him, or, to the best of his knowledge and belief, to any other collector or to any person acting on his behalf or on behalf of another collector, shall be sufficient evidence that the sum mentioned in the certificate is unpaid and due to the Crown.
(5) Any document purporting to be a certificate under paragraph (4) shall be deemed to be such a certificate until the contrary is proved.