I live in Tennessee and my sons mother would like me (the father) to have full custody. I am better able to care for him and want full custody. In the best interest of my son she would like to relinquish custody to him voluntarily. How do we accomplish this? I am on the birth certificate and my son is currently in my care. She would also like to know if it is possible to relinquish all her rights to him voluntarily.

No she can't relinquish all her rights. And why does she need to do anything? You currently have equal rights to your son, he lives with you so you can provide everything needed. There is no reason to do anything, unless you think the mother will change her mind and take your son at some future time.

If that is the case, you petition your local family court to give you full LEGAL and
PHYSICAL custody. If she is willing to sign, then this will be just a matter of the court rubber stamping the agreement.

This would mean she would have to go back to court to get any rights that you do not allow her.

She is quite fickle and will change her mind out of spite. I would like to get this done while she is in an agreeing mood. I am not trying to be conniving or anything like that he is honestly better off with me. I don't want her to be able to yank him away from me and try to use him against me in the future when she's having one of her bipolar moods.

Is there a fee associated with the filing of the paperwork for the mother of my son to voluntairly give me legal and physical custody? We are in Tennessee

First, please don't start multiple threads over the same issue. Its better to keep everything in the same thread. I've merged your threads for you.

Yes, there will be court filing fees involved. They should be minimal. You can check with your local Family Court for what the fees are.

Yes there will be court filing fees, and you will have to have a motion written for the court, normally this will include a parenting plan, custody agreement and child support arrangements.