N.Y. Comp. Codes R. & Regs. tit. 16, § 531.2
If any corporation, partnership or person furnishing water service elects to impose a one-time charge for late payment for such service, it shall show on each bill the amount billed, the amount that will be due, including the late payment charge, when the late payment charge becomes applicable. This section does not apply to residential customers of any waterworks corporation that is covered by Part 14 of this Title.