A claim letter is a formal document sent to request compensation or resolution for a problem, such as a defective product, poor service, or insurance issue. It should be clear, concise, and professional, detailing the nature of the claim, relevant dates, and supporting evidence. The letter typically includes the sender's contact information, a description of the issue, the desired resolution, and a request for a timely response. Keeping a copy of the claim letter and any related correspondence is advisable.