From within the project settings, add them to the project, once they accept, you can transfer it to them.

Thank you brody, I was able to transfer the project to my client. I had a hobby membership while I developed the platform, I asked him to create a hobby membership too, so I canceled my subscription now that I finished the project, could you confirm that now my client is the owner the project would be under his billing account ? So the service wont be interrupted now that I canceled my plan. Thank you.

The project you originally linked when creating this thread is no longer owned by you, but you are still listed as an editor on the project.

From the point that they accepted the project transfer, they will pay for any resources going forward.