How to write a resignation letter that's effective immediately? Use their name and formal title, such as "Dear Mr. Smith" or "Dear Dr. Johnson.The employee should make sure to include their name, current job position, a brief explanation of why they are resigning, and what date their last day will be. Craft a concise, professional resignation letter. Learn how to gracefully communicate your departure without oversharing details. The format of your resignation with a notice period should be a letter. Add contact details, company name, and date.