N.Y. Retire. & Soc. Sec. Law § 45
Upon the employment of any employee whose right to membership in a public retirement system of the state, which for purposes of this section shall include any public retirement system other than the New York state teachers' retirement system, has been made optional by the head of the retirement system involved, the employer shall inform the employee in writing of the right to join the system. Each such employee shall acknowledge the receipt of such notice by signing a copy thereof and filing it with such employer; provided, however, the failure to inform such employee shall not in any way be construed to waive the requirement that membership for such an employee commences only when an application for membership is filed with the system, nor shall it be construed to waive any of the eligibility requirements for previous service credit.
N.Y. Retire. and Soc. Sec. Law § 45