Use their name and formal title, such as "Dear Mr. Smith" or "Dear Dr. Johnson. Use a formal business format for the actual letter itself.Notify your manager in person before you submit your formal resignation letter. A resignation letter is a formal notice stating your intention to leave your job. It typically includes details like your last day and potential next steps. "Learn the essential steps and tips for writing a professional two weeks notice resignation letter. Below is a sample union resignation letter. You should check your union's constitution and bylaws to see if it is specific to whom a resignation must be sent. I am writing to inform you that I will be resigning from my position as (Title) at (Company Name). Be brief, direct and to the point.