Article 5 Adjustment of amounts
A billing authority may authorise a contractor to exercise the functions—
of determining whether on any day (“the relevant day”) after the service of a demand notice the person on whom it was served has ceased to be liable for BID levy;
of calculating the amount payable for the period in the chargeable period up to the relevant day, and preparing and serving on the person who is liable for BID levy a notice stating that amount;
of revising an estimate in a demand notice of the amount payable on the ground that any factor or assumption by reference to which the estimate was calculated is shown to be false;
of preparing and serving on the person who is liable for BID levy a notice stating the amount of that revised estimate and, after deducting amounts (if any) already paid under the original demand notice, the remaining amount due; and
of repaying the amount by which the amounts already paid exceed the revised estimate, or crediting the amount against any subsequent liability of the person for BID levy.