Download a customizable rental application rejection letter template for landlords or property managers to professionally notify applicants. 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.You should always act fairly, professionally, and compliantly when rejecting rental applications. Check out our guide below for the best practices. We discuss everything you need to know about turning down applicants and provide a template for your convenience. Your letter should have a professional and informative tone, covering exactly why you're denying their rental application. Fair Housing Complaint.