Return filing

No it is not mandatory for all PAN holders but for followings

1.Company (i.e.Body Corporate)

2.Person whose accounts are liable to TAX Audit U/S 44AB 

3.Any person whose income has exceeded the basic exemption limit.

4.Any person who is claiming some special deductions

4.Any other persons as mentioned in the provisions.

if you have only salary income you dont need to file incometax return if ur taxable income not exceed 5lakhs

obviously not....

nothing as such.........