Here's what I would do (and have done). 1. Write a letter of resignation. This provides a formal record of termination of contract (if you have one). The least it needs is your last day of work. You can include a brief explanation if you wish. As you have a good relationship, you could include thanks for the opportunity, the working environment, even the good relationship itself; whatever is relevant. 2. Have something planned that you want to say - you don't have to go into a lot of detail if you don't want to, just the salient points. 3. Ask your boss for a word in private. Say you are leaving and give them the letter. You don't have to say much or anything as the relevant information is in the letter, but you have demonstrated respect by meeting in person and can answer any queries. Bear in mind you're not obliged to give any information that isn't pertinent. 4. Presumably your boss knows you stutter, and in any case a manager would read a letter addressed to them anyway. If you're struggling to speak when questioned, any information you want to give should be in the letter so you only need indicate it. Remember that few companies retain an employee indefinitely and you are well within your rights to leave, so keep the courage of your conviction. Focus on the point of the meeting rather than how you speak. Hopefully this should help you leave on good terms.