What is the last date to file income tax for freelancers?

Hey there,

I'm working as a freelancer.  From April 1, 2015 to March 31, 2016 I have made around 17 Lakhs, but I have spent 7 lakhs in business related expenses. 

Can someone tell me what is the last date to file my income tax? Please note: I'm not a salaried professional.  So can you tell me what is the procedure to file income tax and how much its gonna cost for me?

Big thanks.