T-code: FB75 is to enter customer credit memo.
1) Input
Customer: 14454
Invoice & Posting date: 25.02.2021.
Amount: KRW 1,000,000
Text: *TEST
G/L acct: 430501
Amount in doc.curr.: 1,000,000
Text: TEST
Cost center: 97003531
2) Double Click G/L acct: 430501.
3) Input Quantity: 1st & click Back.
4) Input Reason code in Payment.
5) Simulate & save it.