For centralized billing, “ChatGPT business”, (formerly “teams”):
https://chatgpt.com/business/business-plan
I cannot recommend against this highly enough, because OpenAI allows any user seat to invite any other user to your account, instantly incurring the cost of another seat and sharing group resources, damaging your organization security. OpenAI describes the plan starting with the words “A secure”, but it should instead be “a security nightmare”, as you do not have ultimate admin control over the seats and data, and it also destroys user’s existing ChatGPT account data when they are converted or egressed.
You are in the seat usage range where you should be contacting sales@openai.com for ChatGPT Enterprise.