A compound entry uses more than two lines because a single event changes several accounts. The entry still represents one transaction, and its total debits must equal its total credits. Buying equipment partly for cash and partly on credit is a common example. A customer deposit reduced by a processing fee is another.
Calculate the gross amount first, then allocate it. Do not report a net bank deposit as net revenue when a fee explains the difference. You may split an account across several lines when the supporting detail needs it; the checker compares the combined account effect. Avoid combining unrelated events just to make a page balance. Each entry should remain traceable to its source.