Welcome to Community, Robbie.
In QuickBooks Online Accountant (QBOA), there's no option to convert your customers to a client. Instead, we can manually add your customer as a client in your QBOA and delete in if necessary.
If you're syncing regularly between CCH iFirm and QBOA and customers are continuously being created, this manual process may need to be repeated often.
If you have follow-up questions, feel free to click the reply button.