Sometimes your employer will tell you whether you’re being paid cash or in some other way that your work is “off the books.” Your employer has obligations to keep you on the books and if they tell you you’re being paid off the books or even if you’ve agreed to be paid off the books, that does not relieve them of their obligation to pay you fairly, to pay you for all of the hours that you’ve worked and to pay you overtime if you work more than 40 hours in a given week.
Their responsibility is the same whether it’s on the books or off the books and your rights to recover for unpaid wages or unpaid overtime remain exactly the same. Speak to an attorney, help them to understand your case and they’ll tell you what can be done to recover the wages that you should have been paid in the first place.