If I add online payments, where is the option for me to mark up the fee to the customer

Hello sales-intellfire,

Welcome to the QuickBooks Community! I will be delighted to assist you here. You would need to create an item and add the rate. From there, add this as a line item to the invoices. Here is how to create it:

1. Select Sales and choose the Product and Service tab.
2. Underneath the tab, select New.
3. Choose Non Inventory or Service and make the necessary adjustment such as the rate, name, and so on.
4. Save these changes.

The next step would be to click +New on the dashboard and select Invoice. Use the drop-down arrow and select the item you just added to complete the invoice, and that should do it! 

For more information on how to add product and service items to QuickBooks Online, this article is a great reference. If you have any questions or concerns, please let me know! I will be here to lend a helping hand. Be safe!

@sales-intellfire 

QB Payment doesn't offer such feature. Consider having a 3rd party merchant service or payment processor to integrate with QBO.