Annual returns filing for less than 1 lac transaction

We incorporated a pvt ltd company in June 2011. Nil returns were filed for the financial year 2011 - 2012 because no transaction took place that year. For the year 2012 - 2013 ie. till March 31 2013, only around Rs.50,000 transaction has taken place. Do I still need to file NIL returns? How do I calculate the returns to be filed? What is the approximate amount? Thanks.