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.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. If you are open to returning to your position in the future, include that as well. 5.