No stage carriage [shall be used for the carriage of passengers on any road in the State]-
(a) in case any tax or penalty payable in respect thereof remains unpaid for more than fifteen days after the notice of demand referred to in section 9 has been served on the operator, until such tax or penalty is paid, or
(b) in case the returns required by section 4 have not been submitted, if daily returns are required, for more than seven days, and if returns at less frequent intervals have been prescribed for such number of times and during such period as may be prescribed, until the returns are submitted:
Provided that the Tax Officer may, if the operator proves to his satisfaction that the failure to submit the returns referred to in clause (b) was not deliberate, exempt the stage carriage from the operation of that clause.