Normal balance is an intrinsic property of an accounting account, referring to the direction (debit or credit) in which the account's amount increases, derived from the accounting identity 'Assets = Liabilities + Equity', which gives balances directional semantics rather than being simple numbers and allows validation logic to judge whether an entry is reasonable; if the code layer ignores the normal balance classification, it may record a credit on an expense account, producing accounting anomalies such as negative expenses and undermining financial statement compliance.