if you have taken itc at the time of purchased of motor vehicles than you have to pay output tax on sale of used car if not availed itc at the time of purchased then no question of output liability
Vehicle of Vat Regime Sold in GST Regime : GST is applicable on Profit Margin (Sale-Puchase )
Vehicle Purchased & Sold in GST Regime : If ITC claim , then GST is on transaction Value If ITC is not claim , then GST is on Profit Margin (Sale - Purchase)
GST Rate 12 % & 18% is applicable as per CC engine of vehicle mentioned in Notification.
More then 1500 CC , leanth exceeding 4000 MM, GST is 18%