The Financial Industry Regulatory Authority is warning consumers to be careful about using 401(k) plan debit cards to pay for the groceries.

Companies now are selling cards that workers can use to borrow up to $50,000 from their 401(k) plans, or up to 50% of the vested account balance, without having to pay early-withdrawal penalties, according to FINRA, Washington.

“You don’t need separate approval for each transaction,” FINRA says in an alert aimed at consumers. “The total amount that you borrow each day, whether by swiping your card or writing checks, is aggregated and counts as a single loan. You are billed each month for the charges you ring up, plus interest and fees. Interest starts accruing as soon as a transaction is posted to your account–there is no grace period, as there is with some credit cards.”

In addition, consumers must repay 401(k) debit card loans within 5 years or else pay income taxes on the loan balance, FINRA warns.