If you retain a lawyer to represent you in a personal injury case, that lawyer will send a claim letter, also known, as a letter of representation, to the defendant. The claim letter informs the defendant that you have a claim against the defendant and that the lawyer represents you for that claim.
The claim letter is not required by law so it is optional for a lawyer to send it. However, in New York, if the claim is against a municipality or a municipal agency, one must send a Notice of Claim within 90 days of the incident. In some areas, people use the term letter of representation to refer to the contract between the client and a lawyer. In New York, we generally refer to that agreement as the retainer or the retainer agreement.