635.5. Where a supplier refunds all or part of the tax paid by a person in respect of a supply (in this section referred to as the “amount of tax”) to that person under section 635.2 or 635.4, the following rules apply:(1) the amount of tax may be deducted in determining the net tax of the supplier for the reporting period of the supplier in which the refund is made, to the extent that the amount of tax has been included in determining the net tax of the supplier for the period or a preceding reporting period of the supplier; and
(2) the amount of tax shall be added in determining the net tax of the person for the reporting period of the person in which the refund is made, to the extent that the amount of tax has been included in determining the input tax refund of the person claimed in the return filed for the period or a preceding reporting period of the person.