is anyone using a 3rd party app for accepting payments from customers that will automatically charge the processing fee back to the customer at the time of paying

Your client can explore third-party applications in the Apps menu that can offer the functionality to automatically charge payment processing fees back to customers, elaine47.

To help them find a suitable app, guide them through these steps:

1. Go to the Apps menu.
2. In the Find apps tab, use the search bar to look for payment processing apps or fee management solutions that integrate with QuickBooks Online (QBO). They can also explore the Browse categories and Browse industries buttons to narrow down the search. 
3. Review the app descriptions, features, and user reviews to select the app that best meets their needs.

Alternatively, they can visit the QuickBooks Apps Store to explore available options.

If you have additional questions or concerns related to QuickBooks, feel free to share them in the comments below.