Early registration for spring classes through December 29th Payment due January 9th! Early registration for fall classes through August 4th – Payment due August 20th!Our tax calendar helps keep track of deadlines, events and important tax dates on Long Island. First Half General Tax due. Payable without penalty until February 10. First Half 2025 General Tax due. All property tax bills have a payment due date. Payment due date is: March 31 and before June 1. First Half 2024-2025 School Tax due. Sales tax returns generally must be filed no later than 20 days after the end of the period to which they relate.