Discount Received Income in GSTR  - 9

I have purchase vehicle 20 lakhs with gST and party show in GSTR I and next month he shown credit note for discount Rs. 100000 along with GST and i have recevres the ITC in GST and SHow the Discount as Income in INcome Tax and in GSTR -9 all the ITC match in GSTR - 9  buit i want to show that discount Income as expemted ??? or where to show that Discount Received Income in GSTR  - 9???