When people you love and trust ask to borrow your credit card, your better angels might compel you to hand it over—but your better judgment might tell you to keep your wallet closed. It’s likely that tens of millions of Americans have suffered negative consequences  after letting family members or close friends make purchases on their cards.

Compounding the problem is the fact that by loaning the card in the first place, those generous souls were likely enabling some form of financial dysfunction on the part of the borrower.

A recent survey from CreditCards.com examined the issue of card lending, and the results will (hopefully) make you think twice the next time someone asks to take your plastic for a spin, no matter how close your relationship and no matter how seemingly sincere the would-be borrower’s promise to repay.

This survey also brings to mind another recent survey that warned of the risk of getting stiffed if you temporarily pick up a tab for a group of people so you can get extra credit card rewards for yourself.

Card lending is common, but so is getting burned. The study, which polled 2,253 adults living in the US, found that about half (49%) of respondents who have ever owned a card lent it to someone at one point or another. Of those who did, 35% suffered some negative consequence:

  • 19% reported that the borrower overspent.
  • 14% never got repaid.
  • 10% never saw the card again because it was lost, stolen or never returned.

An extrapolation of that data based on the US population suggests that upward of 36 million Americans have gotten burned after lending a credit card to someone they know.

Who is lending, and who is borrowing? The survey showed that of those who lent out cards, one-third handed over the plastic to a spouse or romantic partner. Another 21% lent their cards to their adult sons and daughters, 9% to friends and 4% to coworkers. Millennials, classified as respondents ages 18 to 37, were more likely than older adults to lend their cards, and they were the most likely to say that they had their cards lost or stolen in the process. Those who were generous enough to lend their cards also tended to be generous with their credit. About half said they’d be OK with the borrower racking up bills of $100 or more. About one in 10 said they’d be OK with a purchase of $1,000 or more.

Join the prudent 39%. About four respondents in 10 said they would never let an immediate family member borrow a credit card. That, according to financial experts interviewed by the study’s authors, is the group you want to join. There are a few instances where lending a card might make sense. If a friend with cash in hand is buying a plane ticket and you want the frequent-flier miles, for example, sure, let the friend swipe your plastic if he/she can pay you back right then and there. Barring a few rare exceptions, however, you’ve got about a one-in-three chance of taking a hit if you loan your credit card even if it’s to someone you know and trust. Lending money can be a way to demonstrate love, to shore up relationships or show you care about the borrower’s well-being. On the other hand, sharing a credit card with a significant other can become a point of contention if the relationship crumbles, especially if the card owner is the one most responsible for ending the relationship. And in some cases, if someone needs to borrow your credit card, it may be because that person is desperate. It’s also possible that the person doing the asking is financially dysfunctional, and the moment you hand over that little plastic rectangle, you become an enabler.

What to do: If you do lend your card, be very, very clear about what kind or kinds of things it can be used for, when it must be returned and how much can be spent on it…and possibly require the person to check back with you before using it. Also consider lending cash instead or helping the person get his/her own prepaid card instead—they can be useful for building credit.

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