N.Y. Comp. Codes R. & Regs. tit. 22, § 1215.1
(a) Effective March 4, 2002, an attorney who undertakes to represent a client and enters into an arrangement for, charges or collects any fee from a client shall provide to the client a written letter of engagement before commencing the representation, or within a reasonable time thereafter:
(2) if the scope of services to be provided cannot be determined at the time of the commencement of representation.
For purposes of this rule, where an entity (such as an insurance carrier) engages an attorney to represent a third party, the term client shall mean the entity that engages the attorney. Where there is a significant change in the scope of services or the fee to be charged, an updated letter of engagement shall be provided to the client.
(b) The letter of engagement shall address the following matters: