(2) There shall be calculated the quantity of spirits at proof capable of being produced from any wort and wash made at the distillery on the assumption that from every one hundred litres of wort and wash one litre of spirits at proof will be produced for every five degrees of attenuation, that is to say for every five degrees of difference between the highest gravity of the wort and the lowest gravity of the wash before distillation, and so in proportion for any less number of litres of wort and wash or any less number of degrees of attenuation.

(3) The gravity of the wort or wash for the purposes of subsection (2) shall be taken as that declared by the distiller:

Provided that if either gravity is found by the proper officer before distillation, and the gravity so found is, in the case of wort, higher, or, in the case of wash, lower than that declared by the distiller, the gravity to be taken shall be that so found by the proper officer.

(4) There shall be ascertained the quantity computed at proof of the spirits and feints produced at the distillery after deducting the feints remaining at the end of the last preceding distillation period.

(5) If the quantity calculated under subsection (2) exceeds the quantity ascertained under subsection (4), the excise duty on spirits shall be charged and become payable immediately on that excess:

Provided that the Commissioner may make such allowance as in his opinion is reasonable from any charge under this section on proof to his satisfaction that the charge arises wholly or in part on account of the removal of wash for the separation of yeast.

(5A) Notwithstanding the foregoing provisions of this section, in calculating the quantity of spirits produced at a distillery, the Commissioner may apply such other method as may be prescribed after consultation with the industry.

(6) In this section, the expression "distillation period" means the period prescribed by regulations for the purpose of taking account of feints and spirits produced.