Levy for each month is due on the 17th of the following month (or the next working day if it falls on a Saturday, Sunday or public holiday). If you have missed your payment for a particular month, you will incur penalty charges for that month. 

Generally, penalty charges will not be waived unless there are exceptional circumstances.

If you wish to apply to waive the penalty charges, you need to do it within 1 year of the levy bill.

This information is sourced from MOM