HOW TO RESPOND TO NOTICE U/S 139(9)

I have filed the ITR for salary income but i got a defective return notice under section 139(9) and interesting thing is I have received the refund amount for that ITR and now as per defective return notice there was an income other than salary income due to which I am liable for tax payment, so my query is should i respond to that defective return notice and pay the tax or should I show that income in current year?