Providing the best experience with the product is what we aim for, WandaBenton.

As mentioned above this functionality does not exist in QuickBooks.  To apply the charge to the transaction, you'll need to manually create a service item for the convenience fee. Here's how:

1. Click the Gear icon, then select Products and Services. 
2. Select the New button. And choose Service.
3. Enter the name of the service item (Convenience Fee).
4. Choose the account used for the convenience fee.
5. Click Save and Close.

Then, add the fee as a line item to the existing invoice: 

1. Go to the Sales menu and select the Customers tab.
2. Find and open the customer's invoice.
3. In the Product/Service dropdown, choose the fee item you created.
4. In the Message on invoice section, include a note about the fee. This is optional.
5. Press Save and send.

Just in case you already sent the invoice, we can create a new invoice for the fee and send it to your customer. Here's how: 

1. Tap the + New Plus icon. 
2. Select Invoice.
3. Fill out the invoice.
4. In the Product/Service dropdown, choose the fee item you created.
5. In the Message on invoice section, include a note about the invoice the fee is related to. Also include the invoice number.
6. Press Save and send.

Feel free to visit our Invoices and payments page for more insights about managing your invoices on your account. 

If you need to take care of other things in QuickBooks, I'm with you every step of the way. Just leave a comment below and I'll get back to you. Take care always.