Think twice if it looks as if someone is sending you free money. The mail recently carried envelopes to credit card holders with the notation “Check Enclosed”

on the outside. Inside was a check for $15, payable to the addressee. Sounds like manna, doesn’t it?

Well, some faint small print on the back, just ahead of the place for endorsement, carried news that could easily be missed. It said, “Signing, cashing and/or depositing of this check will enroll you in optional Credit Protector. The monthly fee will be automatically billed to your account.”

The New York Times reported a similar incident last month. A Houston chiropractor had cashed a $2.50 check last December from Yellow Pages Inc. of Anaheim, Calif. He took it to be a refund from an overpayment for advertising in the local telephone book. But the next month he got a bill for $179 from the Anaheim company for registering his health center with its electronic directory, The Times reported. It was another case of not reading the fine print.

Such scams, deceptive though some may be, are technically legal and are tracked by the Federal Trade Commission. The agency’s latest report says losses totaled more than $437 million in 2003. The agency asks victims to report any suspected swindles. While it does not seek justice in individual cases, it builds its database to keep track of a growing national problem. Its Internet site, www.consumer.gov/sentinel, provides a secure reporting form.

For the individual, the best advice is the old saying, caveat emptor, or let the buyer beware. Or, in this case, let the payee beware.