1. In the sample letter, fill in your personal information. A credit dispute letter includes personal information and enclosures that help credit bureaus investigate mistakes.Fill out a credit dispute letter and include supporting documents. These are the actual letters I have sent. I'll note the situations for each letter in red. Formally disputing an error involves writing a formal dispute letter to the creditor as well as the appropriate credit bureau reporting the inaccuracy. Add an enclosure notation after your signature at the end of the letter, and abbreviate it with "Enc." or "Encl. Financial Services Account Number as provided in the Financial Services. Delivery Instructions available in CITSS. Take precaution to completely fill out each item of this form.