Dear Ms. Emily Clarke,. How to write a resignation letter that's effective immediately?Dear (HR Manager's Name),. "I received your request that I submit my resignation in writing. Hi,. Please be advised that I am resigning my position with immediate effect. Regards,. (For example, "I regret to inform you that I will be resigning from my position, effective immediately. At the beginning of your letter, consider immediately describing your intention to resign. You should never sign a resignation letter under duress. It is with regret that I have to resign my position as a nurse practitioner in the cardiac unit at UPMC East immediately. Please accept this letter as my formal resignation.