(NewsNation) — Remember that gift card you got last Christmas but never used? Other people are forgetting about theirs, too — and it’s making for a windfall for businesses and restaurants.

Whether it’s in their junk drawer or wallet, Americans are holding on to $21 billion in unused gift cards, according to a CreditCards.com survey. About half of all Americans, the poll found, have a gift card they didn’t redeem.

“It’s completely free money for the companies,” finance influencer Daniel Iles said. “It seems like a fair trade dollar for dollar, but really, it’s not and there’s a lot of profit to be made from selling gift cards because many of them go unused.”

There’s even a holiday in honor of people’s forgetfulness: “National Use Your Gift Card Day” is Jan. 21.

“Consumers, if they do give gift cards, need to be sure that the people who they’re giving them to actually know what to do with them. And especially, that applies to digital gift cards,” John Quelch, dean of the University of Miami’s business school, said. “If you send one to your grandmother, you may not be absolutely sure that she’s going to be able to claim it.”

Federal rules mean gift cards can’t expire for five years — but businesses can deduct fees if the card is inactive for 12 months.

Some individual states have additional rules as well.

“Kind of a harsh reality — you should probably get more creative with your gifts,” Iles said.