Official Letter No. 4991/TCT-CS dated November 5, 2024, issued by the General Department of Taxation
In principle, trade discounts based on the quantity or sales volume of goods and services are adjusted on the invoice for the last purchase or the following period. If the discount amount is determined at the end of the sales discount program (period), an adjustment invoice is issued along with a statement listing the invoice numbers that need adjustment, the amount, and the adjusted tax. Based on the adjustment invoice, the seller and buyer declare the corresponding adjustments in revenue and tax.