friend normally persons taking pan no. for showing identity proof . but major cases it was seen that it. department started notices to new pan no. alloted under uti scheme or nsdl scheme for filing of return. therefore it is better to file return even thought person have non taxable income if he/she has pan no.
While its not compulsory to file returns if you have income below the taxable limit I would advice to file a Nil Return also (whats the harm) and incase you have losses then please file returns to claim the set off and carry forward in the following years.