Restriction on the use of taxable vehicle in certain cases

No taxable vehicle shall be plied in the State- (a) in case any tax or penalty payable in respect thereof remains unpaid for more than fifteen days, until such tax or penalty is paid, or (b) in case the returns required by section 6 have not been submitted, until the returns are submitted; Provided that the prescribed authority may, if the owner proves to its satisfaction that the failure to submit the returns referred to in clause (b) was not deliberate, exempt such vehicle from the operation of this section.