If an individual's income is below the taxable slab of Rs 2.5 lakh currently, it is not mandatory to file income tax return for him/her. However, if you have a PAN (Permanent Account Number) card and an income that is below the taxable threshold, experts advise them to file the ITR with a NIL return. This way you show to the IT department that you did not have any taxable income for a specific financial year and therefore, you did not pay income taxe for the same.