Hi there, os-dieselrepair.

For now, we're unable to automatically charge customers with a convenience fee. We'll have to set up a non-inventory or service item to enter the credit card fee. 

Here's how: 

1. Go to the Sales menu and select Products and Services. 
2. At upper-right, click New. 
3. Select Non-inventory or Service as the item type. 
4. Enter a Name something like Convenience Fee. 
5. Select the correct Income account and then Save and close. 

When we create a sales transaction, we'll need to add the Convenience Fee item. Having this feature to automatically assign a charge saves time. I personally sent this feedback to our engineers and we can add it to our future updates. 

Let me know if you need anything else. Thanks!