How can I setup my invoices to have the customer pay any transaction fee?

I'm delighted to see you here in the Community, @wjddesign.  I'll show you how to add a transaction fee to your QuickBooks Online invoices.

You can add the payment processing fee to your customers' invoices and charge them for it.

The payment can be paid with a service item. To do so, follow these steps:

1. Select Products and Services from the Sales menu.
2. Select Service after clicking on New.
3. Enter the name of the service item you're providing. (An example of a credit card fee)
4. Under the Income account drop-down, choose the account you'll use to track our processing fees.
5. When you're finished, click Save and Close.

Whenever time you charge your clients a processing cost, include the created fee as an additional item on your invoice.

Check out this post to learn how to send customers reminders when their invoices are about to go past due.

Return if you have any further questions concerning your QBO sales transactions. Have a fantastic day!  

@wjddesign 

QB Payment doesn't yet offer such option. Consider to have a 3rd party merchant service or payment processor to integrate with your QBO.