From the dashboard go to the customer tab

Select the specific customer to go to their customer profile

At the bottom of the page you will see all the invoices for that customer

Click on Batch Process

This pop up will appear allowing you to select the invoices you want to process

With a credit card inserted and the surcharge box checked you will see a change in all of the totals

With the surcharge box unchecked the percentage will be listed as 0.00 and all of the totals will be what the originally were

If a debit card is inserted the percentage will read ineligible

You will get notified that they were successfully processed

The invoice details will be marked as paid and the surcharge fees will be added for each invoice processed