80Charge on percentage of turnover
(1)Where it appears to the inspector or, on appeal, to the General or Special Commissioners, that the true amount of the profits or gains of any non-resident person chargeable with income tax in the name of a resident person cannot in any case be readily ascertained, the inspector or Commissioners may, if he or they think fit, assess and charge the non-resident person on a percentage of the turnover of the business done by the non-resident person through or with the resident person in whose name he is chargeable as aforesaid, and the inspector may by notice require the resident person to deliver a return of the business so done by the non-resident person through or with the resident person.
(2)The amount of percentage under subsection (1) of this section shall in each case be determined, having regard to the nature of the business, by the inspector or Commissioners.
(3)If either the resident person or the non-resident person is dissatisfied with the percentage as confirmed or determined by the General or Special Commissioners on appeal, he may within four months of the determination, require the Commissioners to refer the question of the percentage to a referee or board of referees to be appointed for the purpose by the Treasury and the decision of the referee or board shall be final and conclusive.