Unlike normal retirement letter, voluntary retirement letters are important to approve your quitting from job. It is important for voluntary retirement letter to be formal, polite, and respectful.
This is to inform to you that I want to take a voluntary retirement from my position as senior marketing manager, although I have 6 more years of service in the company. Due to the reason of my health issues and family wishing to settle in my native place for the rest of my years, I will not be able to continue my job in your company.
It was a pleasure working with you all for the past 15 years and am humbly grateful to the organization for providing me the opportunity to learn and grow. I believe you will respect my decision to voluntarily retire ahead of my service period, and grant me permission to move on with the retirement procedures. Kindly consider this formal letter date of my voluntary retirement as the beginning of my notice period of 1 month.