Definition of Comfort letter

A comfort letter is a document prepared by an accounting firm assuring the financial soundness or backing of a company. The comfort letter can be issued by a CPA declaring no indication of false or misleading information in the financial statements and that the company's prospectus follows GAAP. This is sometimes used in connection with an initial public offering. Comfort letters are also sometimes provided by those involved in evaluating a company's assets, for instance, in the case of oil and gas companies, third-party reserve engineering firms.