Post sale discounts: classify as supply related or service consideration; GST and input tax credit consequences follow accordingly. Post sale discounts must be classified by commercial substance: unconditional discounts relating to the original supply may be excluded from the supplier's taxable value if statutory conditions are met; discounts contingent on dealer promotional activities constitute consideration for services by the dealer and attract GST with corresponding input tax credit for the supplier. Discounts paid to enable dealers to reduce customer prices are consideration for the dealer's supply and must be added to the dealer's taxable value; recipients' input tax credit is limited to tax actually paid. Financial/commercial credit notes may be issued where exclusions are not permitted but do not allow the supplier to reduce original tax liability; dealers need not reverse input tax credit if they adjust payment as required.