By Percentage:

1. Go to System Manager | Activities | Company Configuration
2. Click the System Manager menu
3. Scroll down to the Credit Card Processing section
4. On Credit Card Processing section | Credit Card Convenience Fee field, select Percentage
5. Enter the percentage value corresponding to the listed card type/s with convenience fee.
   • Visa
   • Mastercard
   • American Express
   • Discover
   • Diners Club
   • China Union Pay
6. Enter the Fee General Ledger Account field value
7. Enter the Payments Location field value
8. Click the Save button. 

None:

1. Go to System Manager | Activities | Company Configuration
2. Click the System Manager menu
3. Scroll down to the Credit Card Processing section
4. On Credit Card Processing | Credit Card Convenience Fee field, select None. This will disable both the Percentage and Fixed Amount columns.
5. Click the Save button.