Section 143(1)

As per sub-sec 143(1), last proviso... the time period is 12 months and not 6 months... Read

"Provided further that no intimation under this sub-section shall be sent after the expiry of one year from the end of the financial year in which the return is made."

i.e. the intimation must be issued within one year from the end of the year in which return has been filed. For example, if you have filed your returns for Assessment Year (AY) 2016-17 on 27 July, 2016, (i.e in the FY 2016-17) then an intimation can be issued anytime on or before 31 March, 2018.

As per current income tax laws, under 143(1) the time limit to process ITRs by the tax department is within one year from the end of the financial year in which ITR was filed.

Thus, your ITR must be processed by March 31, 2021 for the return filed for FY 2018-19.

Once your ITR is processed, the income tax department sends you an intimation notice.

I concur with Shri Rambhia.