Post sales discount :

Section 15 of the model GST bill deals with valuation of taxable supply and clause (h) of sub-section (2) allows only those discounts to reduced from the value of supply that can established as per the agreement of supply and is known at or before the time of supply. It also requires that such discounts should be specifically linked to relevant invoices and therefore, excludes any lump-sum discount. The adjustments for post sales discount will be completed before filing of annual return. The credit/debit note will be reflected in the monthly return in which the said adjustment is made.