How many last previous year return files in this year?

Chetan (M.Com) (32 Points)

25 August 2015  
My friend father would be retired in the year 01/06/2011. He has received monthly pension from central govt. & under the income tax slab rate non taxable. But he has not return filled after the retirement. My question is can I possible to fill the return for those previous years missed? What is due date for missed return submitted?