You could have $100 waiting in the mail. Don't throw it away.

JACKSONVILLE, Fla. – People could be leaving hundreds of dollars on the table because they think it's junk mail.

Valpak sends out $100 checks to people across the country every month -- no purchase necessary, no strings attached, just a check made out to cash. Sounds like easy money, right?

Sure, but the trouble is that most of the checks go unclaimed. In fact, only 7 of the 36 checks mailed to those in the Grand Rapids, Mich. area last year were never cashed, according to WZZM-TV.

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The $100 Instant Win program is nothing new, either. It turns out Valpak has been doing this on a smaller scale since 1988. But 2018 marks the first time the promotion is going nationwide.

To make things easier on people this time around, Valpak is randomly placing those $100 checks inside specially-marked envelopes that literally tell you: "Look inside. $100 could be in this envelope!"

So before you chuck that stack of junk mail, check to see if there's a Valpak envelope in there. You could win some easy money.