143(1)-Intimation

One of the assessee has received intimation for Demand from CPC, where the CPC does not consider 80C deduction.

Now i have prepared a Letter of Reply for rectification of mistake u/s154 and enclosed a xerox copy of LIC Premium Paid Receipt. The assessee is in USA at present so i cant get signature from the assessee . Whether i can get signature from the father of the assesse as representative assessee and send it to CPC?