Thank you for your help.
Here is the other problem. When I issue the credit memo, it will offset my sales account and leave a negative amount in Accounts Receivable.
So when I apply the credit, it should affect accounts receivable balance (goes up) and clear the negative amount in AR.
But when I check the transaction journal, it did not affect the AR. The credit is applied but the balance of AR is still the same. Please advise.