Post-sales discounts under GST: conditional incentives treated as payment for dealer services, unconditional discounts adjust supply value. Post-sales discounts are governed by the valuation provisions and may be excluded from the supplier's value of supply only if granted without further obligation by the dealer and the conditions for adjustment are met. If the discount requires the dealer to undertake promotional activities, it is consideration for a separate supply of services by the dealer, on which the dealer must charge GST and the supplier can claim input tax credit. Payments by a supplier to enable a dealer to offer reduced customer prices form part of the dealer's value of supply. Where a supplier issues financial/commercial credit notes because exclusion is not permitted, the supplier cannot reduce original tax liability; the dealer need not reverse ITC provided the dealer pays the reduced value after adjusting credit notes and the original tax charged.