Navigate to QuickBooks and add a new invoice, as usual

Click the "Separate emails with a comma" field.

Click "Save" or "Save and send", and follow your usual process to distribute the invoice. When your customer receives the invoice, both the email and the PDF will have a link for payment included. 

They just need to click this link to make a quick and easy bank payment, and the invoice will be automatically marked as paid when complete.

https://e-pay.fena.co/pay/?p=wzYr85oEXBCnGRgB5oZr

QuickBooks

Creating an invoice with a Fena payment link