without being included on official financial records.
Waiters, cashiers, and busboys often work off the books, getting paid in cash.
Usage notes: sometimes used with keep or take:
Officials have kept their expenses off the books.
off the books
Off the official payroll; paid in cash, without any official employment paperwork. I worked off the books in my uncle's restaurant for a few months during the summer.It's no secret that many migrant workers are kept off the books at major agricultural and construction operations around the country.
on/off the/somebody’s ˈbooks
(business) included/not included in the official financial records of a company: The company falsified its accounts and kept billions of dollars in debt off the books.