Your letter should have a professional and informative tone, covering exactly why you're denying their rental application. If a landlord denies your application, they're required to tell you why in writing.This is called a "notice of adverse action." The landlord must give you a written notice stating their reasons for denying your application. Download a customizable rental application rejection letter template for landlords or property managers to professionally notify applicants. Our forms and sample letters use "unlawful detainer.