Independent contractor (how to calculated tax)

Hi Experts,

I am survey programming expert. I am working from home for US based firm since sep 2011. I am getting salary approx $2k monthly. I got around 270000 till sep from my past company as salary.

May I know how should i fill the tax for this year. I already have filled tax till sep2011 when I was part of last company which has office in India but I didnt filled any tax after sep as I joined the firm which don't have any office in india. Working independently from home.