Notice under 156 ?????

Notice under section 156 is a demand notice you need to reply the notice with in 30 days form the date of issuance of notice. You need to know the reason for the demand by applying intimation under section 143.1 of income tax act if u file online return than intimation can be called online so that you can compare your return as per per your records and as per IT records and get to know the reason. If you think demand is valid you pay the tax and make a reply and submit to your respective ward if not then u can file rectification u/s 154 of IT act (Online in case of online return) other wise you have to purse department for the same.