25 March 2013
Better to send it through registered post. If you e-filed such return then you can submit your rectification request teturn through online.
26 March 2013
You send the register post with acknowledgement. On that acknowledgement you write the details of your letter example of the matter to write is as follows.
We received the 154(1) rectification letter for Pan no:XXXXXXXX, A.Y XXXX-XXXX through registered post no XXXXXXXXXXX and the same has been acknolwedged with it.
Then the receiving person shall make sign on such acknolwedgement with stamp and re-post such acknowledgement to you by the post office. As well as you can trance the online status of your delivery of registerpost at www.indiapost.gov.in