Problem
You want to add a credit card fee to the customer's invoice.
Solution
Create a fee in Pricebook under Discounts & Fees. Add this fee to the customer's invoice.
Create a fee in Pricebook
Go to the navigation bar and click Pricebook.
In the side menu, click Discounts & Fees.
Note: Account configuration is required to use Discounts & Fees feature. Please reach out to your Customer Success Manager (CSM) for details.In Discounts & Fees, click Add Discount or Fee.
In the Add a Discount or Fee screen, select Fee from the Type field.
Set up the fee with the following details:
Name: Credit Card Fee
Add a percentage or fixed amount.
Description: Fee for credit card payments
When finished, click Save.

Open the specific customer's invoice.
Click Add a discount or fee.

Click Save. Now, the credit card fee is added to the invoice.
Tip: If you want to automatically charge for credit card fees, assign a default service for each job type to remind you to charge the fee manually. For more, see Add default services for job types.