In that case, what would be the position of A vis a vis the Sales Tax Officer demanding the tax ? Could A escape liability, if he failed to collect the tax from B at the time of the sale ? Or is A to collect the tax, ignoring B 's declaration of his intention to export and leaving him to apply for refund by producing evidence of actual export, whenever that takes place? Even if a sales tax enactment provides for adjustment on those lines, would not such legislation, in so far as it compels B to suffer the tax until he actually exports the goods, contravene clause (1)(b) which ex hypothesi exempts the transaction from sales tax? And what would be the position if the goods were burnt or otherwise lost in the meanwhile, and the export never took place? Athough, as pointed out in the previous decision, American cases are not of much assistance in interpreting article 286 because of the different wording of the import export clause of the Federal Constitution, it is interesting to see that such uncertainties led the American courts to lay down the rule that "It is the entrance of the articles into the export stream that marks the start of the process of exportation.