But before you make one more purchase, counting on that rebate money, we have a warning for you.

When Harry Levy bought his laptop computer, he tried to save a little money by getting one that offered a rebate.

"I ordered the items online and you can only order it online to get the rebate -- at the end of February," Levy said. "It didn't ship 'til the first week in March, and because it shipped after the rebate period, they denied my claim."

Harry wasn't going to take no for an answer. But he says it took months of phone calls to get his money.

"By the time I got the rebate, it was the end of August," he said.

Consumer Reports' Kim Kleman says many companies make rebates too hard to redeem.

"You have to jump through a lot of unnecessary hoops to get a rebate. In many cases it's more like 'rebate and switch,'" Kleman said.

Often to qualify for a rebate, you need the original receipt, a bar code from the package, and the rebate form.

MORE ON THIS STORY ConsumerReports.org To file a complaint, go to ftc.gov

Sounds fairly straightforward, but you can run into trouble pretty quickly.

"You have one original receipt for three separate rebate items, for example, or the bar code is on the box you've already thrown away, or the claim slip you were given has expired," Kleman said.

Companies use rebates to encourage you to buy. But the math works in their favor. It's estimated 60 percent of rebate offers are never redeemed.

Rebates are such a popular selling device for companies, they offer $10 billion worth every year.

Still, because of deceptive policies by many of those companies, the Federal Trade Commission has brought a number of criminal cases against them for mishandling the rebate process.