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. First, clearly state the reason for the appeal of the property's decision and restate their reason for denying your rental application.Download a customizable rental application rejection letter template for landlords or property managers to professionally notify applicants. You should always act fairly, professionally, and compliantly when rejecting rental applications. Check out our guide below for the best practices. Below we outline some of the common reasons why a rental application may be denied, and how you can fix them. Under this new law, it is illegal for a landlord to refuse to rent to someone solely because they received rental assistance within the past two years.