Post sale discounts: treated as supply value or separate service depending on dealer obligations and GST implications. Post sales discounts affect the value of supply and must be classified by examining whether the supplier imposes further obligations on the dealer. Discounts without dealer obligations relate to the original supply and may be excluded from the supplier's taxable value if statutory conditions for exclusion are met. Discounts that require promotional actions by the dealer constitute a separate supply of services by the dealer, on which the dealer must charge GST and the supplier may claim input tax credit. Where statutory exclusion is not permitted, suppliers may issue financial/commercial credit notes but cannot reduce their original tax liability; dealers need not reverse ITC if they adjust payments in line with the credit notes and original tax charged.