How To Write A Letter Of Concern To A Company . Use a simple, professional, complimentary close, such as sincerely or regards. You can mention the purpose of the letter in the subject line. AuthorisationLetterFormatToCollectDocumenAuthorizationLetter from ryanjlima.com Focus on the objective facts rather than on how you feel about the situation. Your employer’s grievance procedure should set out the person who deals. Method 1writing your complaint letter.