Gst on fright subsidy

Freight subsidy from the supplier would be for a period. It is akin to a discount as it reduces the total amount payable to the supplier. The supplier would have included GST when he billed. The subsidy would be passed by way of a credit note. The important question is whether he added GST also.

Ex FS = 100 did he simple send a CN for 100 or 100 + 18 (GST). Ideal would be that he should only raise CN for 100 so there is no impact of GST on him or the customer + importantly no adjustments in the returns for both cusotmer + supplier.