In the letter, express your appreciation for the applicant's interest and politely explain why you declined them. In your letter, you should politely decline the applicant.Under federal law, a landlord who denies your tenant application because of information in a tenant screening report is required to inform you of that fact. 4. Bad credit report. What Can't a Landlord Ask in a Rental Application Form? One of the first things successful landlords tell anyone considering renting out a property is to always select good tenants. Each adult (18 years of age or older or emancipated) must complete and sign the Rental Application. A rental application denial letter, also known as an adverse action letter, is a formal document that a landlord or property manager sends to applicants.