Evidence of unpaid tax
7(1)A certificate of an officer of the Board—
(a)that tax is due and payable, and
(b)that to the best of his knowledge and belief payment of the tax has not been made,
is sufficient evidence that the sum mentioned in the certificate is unpaid and is due to the Crown.
(2)A document purporting to be such a certificate shall be deemed to be such a certificate unless the contrary is proved.