Your application must be filed with the Board of Assessors by December 15th or 3 months after the actual tax bills are mailed for that fiscal year. The normal time frame for filing starts as of July 1st and ends three months after the actual tax bills are due. This deadline can't be extended for any reason.
Filing an application does not stay the collection of your taxes. To avoid the loss of rights or additional charges, you should pay the tax as assessed. If there is an overpayment due to the exemption, you will be issued a refund.