Ok, as we say in French, my answer will be a Normandy answer (réponse de Normand). Meaning that this answer will not be a black 'n white answer variety.

If you choose to terminate as a client who comes voluntarily, there is no right or wrong way to terminate.
It depends of how do you feel with your T and the therapy.
It's a whatever works situation : if you choose to terminate with your T, what you do is not written in the stone.

If your therapy is Court-ordered, that's an entirely different ball game. Since I don't have the slightest scooby, I gladly leave my seat to more competent folks here.

Rules for termination are body licensing regulations for therapists. If your T chooses to terminate, he has to follow his professional regulations for not being liable of abandonment.

OTOH, if a client who comes to therapy voluntarily chooses to terminate, he is free to terminate.
You owe nothing to your T. You hire your T, your T doesn't hire you.

If you feel comfortable with giving your T a N time notice before termination, it's the most important.
No one holds the universal truth about how to terminate with your T because this situation doesn't know the universal truth.

The way you terminate the T you voluntarily see is your freedom of choice.

The only rules you have to respect in terminating your T is the basic common sense like no physical violence, no uttering threats etc...
Aside from these rules of basic common sense, I repeat that the way you choose to terminate the T you see voluntarily is your personal freedom.