I've been trying to journalize this and think I've got it wrong:
Assume a 4% service fee is charged by American Express. Record the entry for the transaction on the restaurant's books for Dr. Miller’s AMEX credit card transaction.
The service fee is 2,000 x 4%=$80. The entry is
Accounts Receivable – American Express Dr $1,920
Service Charge Expense Dr $80
Revenue Cr $2,000
