Article 9 When a debt is liquidated by cash, the creditor shall include the difference between the book balance of the debt to be restructured and the cash received in the current profits and losses.
第九条以现金清偿债务的,债权人应当将重组债权的账面余额与收到的现金之间的差额,计入当期损益。
This leads to another important concept called 「accrual accounting.」 When many people start keeping books, they simply record cash received for services rendered as revenue.