Learn how to write a professional resignation letter with our step-by-step guide, easy to use templates and helpful tips. 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. We've rounded up tips and examples for writing a resignation letter that'll help you maintain work relationships long after leaving a company. "Learn the essential steps and tips for writing a professional two weeks notice resignation letter.