Hi, @Jonnika.

The option to automatically apply credit card processing fees is currently unavailable in QuickBooks Desktop (QBDT).

In the meantime, you can add the fee as a line item on your sales forms. Let me guide you through the process.

1. Go to the Lists menu, then select Item List.
2. In the Item dropdown, choose New. 
3. Pick Service from the Item Type dropdown.
4. Input the Sales Price and specify the Income and Expense accounts.
5. You can also enter "Credit Card Charges" as an Item Name.
6. Once done, hit OK.

We understand the importance of having the option to add credit card processing fees for accurate cash flow. However, due to the variability in how each state handles credit card surcharges, this feature is currently unavailable in QBDT.

To help improve your experience with QBDT, your valuable input will be shared with our product development team. Here's how to send it:

1. Select the Help menu, then Send Feedback Online.
2. Choose the Product Suggestion option.
3. Enter your comments.
4. Click the Send Feedback button.

Here's a helpful article to refer to if your customer's credit card payment gets declined during processing: Fix customer's declined credit card payments.

I'm always here to back you up if you have further concerns about applying credit card processing fees. Feel free to hit the Reply button.