If Asseessee's Gross Total Income less than BEL* then no need to file his ITR as per sec 139(1)... Thus, As per sec 139(1) every Assessee must file his ITR if income based on said section. Assessee's Gross Total income exceeds BEL then He ll file on or before due date**
If not filed then sec 234F levied.
* BEL means Gross Total Income (Before all deductions and Expenditures).
** Due dates will be applicable as per extended notifications
If the gross total income, means income before providing any deduction, is below the basic exemption limit, you are not required to file Income tax return. And as per Sec 234F, the penalty is for the person who is required to file the returns as per section 139. So since people having income below BEL are not required to file returns, they can escape this penalty provision. But not sure whether it can be taken to this literal level.