Convenience Fee --why was I able to add that option to one of my QB online accts but not the other?

Hi there, thestay.

Welcome back to the QuickBooks Community. I'll ensure to share details about convenience and other transaction fees in QuickBooks Online and how it works.

The option to add a convenience or credit card fee automatically on the transaction is unavailable. There are cases that a business that can charge customers a convenience fee for using a credit card. That said, QBO has a QuickBooks Payments feature that you can turn on online payments for the invoices you email to customers. I suggest making sure that you have this payment account in your QBO so you can do more than just track your accounting. With QuickBooks Payments, you can accept credit card, debit, and ACH bank transfers for invoices you send. Then, where it allows your customers to pay online with the fees already charged to it. 

Please note that once you use QuickBooks Payments to take payments from QuickBooks, there's a processing fee. Always check the QuickBooks Payments website for the latest processing fee rates and pricing. QuickBooks Payments charges a fee each time you process a transaction. Fees also depend on how you processed the payment. You can click this article to see further details: What are the fees for QuickBooks Payments?.

Please also refer to this article to see how QuickBooks Payments deposits work in QuickBooks Online: Common questions about payments deposits in QuickBooks Online.

Don't hesitate to post again here in QuickBooks Community if you have additional questions about fees. I'll be right here to help. Have a great day!