9 Payment of the excise duty
1 The Commissioners may require in writing a person liable to pay the excise duty by virtue of regulation 6 above, or 7 above, to pay that duty and, where they do so require, they shall specify in that written requirement the amount of duty that is to be paid.
2 A person required in accordance with paragraph (1) above to pay the excise duty shall pay immediately to the Commissioners the amount of excise duty specified by them upon receipt by that person of the written requirement specifying that amount.