N.Y. Comp. Codes R. & Regs. tit. 22 § 500.6
Counsel shall timely inform the clerk's office and each other party by letter of all developments affecting appeals, section 500.27 certified questions, motions and criminal leave applications pending in this court, including contemplated and actual settlements, circumstances or facts that could render the matter moot and pertinent developments in applicable case law, statutes and regulations. For appeals, counsel shall also timely inform the clerk's office and each other party by letter of any changes in the status of any related litigation reported on the appellant's preliminary appeal statement or of any related litigation commenced after the filing of appellant's preliminary appeal statement. Such letters shall contain proof of service on each other party.
N.Y. Comp. Codes R. & Regs. Tit. 22 § 500.6