Is it necessary to file returns for AY 2011-12 if the total income is less than Rs.5 lakhs and no refunds are expected

You need not file the return if all your sources of income and deductions have been mentioned in the form 16.But if you have other sources of income or some deductions likeFD, capital gains etc not covered under form 16 then you better file the return.

More details here: http://www.investmentyogi.com/taxes/no-need-to-file-tax-return-for-income-up-to-rs-5-lakh.aspx