off the books; unaccounted
Used in accounting and finance to describe assets, liabilities, or transactions not recorded in official ledgers. Often implies hidden or unofficial handling.
It was discovered that the company had off-the-books debts.
Off-the-books transactions become an issue in accounting audits.
Compound of 簿 (bo, 'ledger, record book') and 外 (gai, 'outside'). Literally 'outside the ledger'.