Application for rectification u/s 154

Dear Sir,

One of my client received Intimation U/s 143(1) for A. Y. 11-12. which states for tax liability to be paid. This arise due brought forward loss not shown in CYLA BFLA but reflected in CFA. Date of order is 20.01.2012.

I want to know whether I should file Application for Rectification U/s 154 or file revised return for the same.

Kindly let me know if any other related provision need to be considered.

Thanks