While making outward supply seller include commission on total taxable value and GST is liable to charge on such value by respective percentage of their outward supply. If commission collected by agents or broker within meaning of sec 2(5) of CGST act then 18% gst charged on such commission. If amount of commission payable(excluding GST) to particular agent exceeds 15000 p.a. then sec 194H of I.T. act 1961 applies and 10% TDS have to be deducted. Such TDS should be deduct without considering GST amount.
The Article 366 (12A) of the Constitutional (101st Amendment) Act, 2016 defines
“Goods and Services Tax” as any tax on supply of goods, or services or both,
except for taxes on the supply of the alcoholic liquor for human consumption.