Hello there, @invoices88.
Let me add some insights about multiple companies in QuickBooks Online (QBO).
You can have multiple companies under your QuickBooks Online account. Each company you add will be a separate paid subscription. Since you mentioned that you already have five companies, you can move them all under one account if they are under separate accounts in QBO.
You can use this article for the detailed steps on how to use one email and user ID for all the QuickBooks Online companies you sign in: Use one user ID for multiple companies.
You can also use this article If you add more companies in the future: Add companies under an existing user ID.
If you have other questions, please don't hesitate to go back to this thread. Take care!