Dan Ring of Milton tried to write a check for $150 worth of gift cards at Macy's just before Christmas, but the retailer wouldn't accept it.
The person operating the cash register told Ring his account had been flagged for some reason, and he might want to contact his bank.
''You think, 'Oh my God,' " why are my checks being flagged?" said Ring, who worried that somehow a negative rating had popped up on his credit report or someone had stolen his identity.
As Ring set out to find out what had happened, he discovered that retailers such as Macy's employ check authentication companies that take the limited information gathered at the register and in about a third of a second decide whether the check being offered for payment should be accepted or rejected.
The companies rely on massive check-transaction databases and fraud modeling systems to make each call. Officials at the companies say less than a half percent of the $790 billion of point-of-sale checks written each year are rejected.
''The last thing we want to do is turn down the transaction and ruin the relationship with the retailer," said Stephen Kuzio, vice president of business systems development at Certegy Inc., a St. Petersburg, Fla., company that handles check authentication for Macy's, Best Buy, Sears, Roebuck & Co., and many other retailers.
But when rejections do occur, sometimes mistakes are made. Scattered complaints have popped up on online forums about check rejections that occur for reasons that are hard to fathom. Usually the consumer is given some vague explanation about his or her check falling outside the authentication company's risk parameters.
In Ring's case, he checked with his bank, Citizens Bank, after the Macy's rejection and found nothing amiss. He also checked his credit reports. He learned about Certegy's involvement from an employee at Eastern Mountain Sports in North Conway, N.H., after a second check was rejected there.
Ring's wife, Dolores Kong, a certified financial planner at Winslow, Evans & Crocker in Boston, called Certegy for an explanation and was told the checks were rejected because they were the first her husband had written at those retailers, a Catch-22 that made no sense.
According to Kong, the Certegy representative suggested that Ring and Kong might want to apply for a special VIP status with Certegy. On its website, Certegy has a Gold application, which the company describes as ''your ticket to quick and convenient check writing."
Certegy Gold applicants have to provide detailed information about themselves, their employers, and their bank, including a voided check. Gold status doesn't cost anything, but members agree to pay a service fee to Certegy each time they write a ''dishonored check."
''It's bad enough worrying about your credit and identity theft protection in this day and age," Kong said. ''Now we have to worry about check approval services that deny without any reason, and then turn around and push a Gold membership on you so you're in their database."
Macy's officials referred questions to Certegy. Kuzio told the Globe there must have been a miscommunication by the company's representative, saying first-time check writers are not routinely rejected.
He investigated what happened and subsequently apologized to Ring for the improper check rejections. Kuzio also offered him a $100 gift certificate to Macy's and flagged his name in Certegy's computers so another rejection would not occur.
Ring said Kuzio told him that something about Ring's identifying information was ''eerily similar" to data associated with a fraud ring using Citizens Bank that had been purchasing gift cards and sports equipment.
''He said the accuracy of his system is very good, but in this case it was wrong," Ring said. ''It sounds like a case of mistaken identity. I feel this tremendous sense of relief."
The online auction site says it makes every effort to make sure its customers comply with the various state laws on ticket scalping across the nation, but a review of tickets on sale last week indicated the rules are not always enforced.
EBay does more than most ticket websites.
According to rules posted on eBay, Massachusetts residents selling tickets on the website are required to list the tickets' face value.
Bay State residents are also prohibited from selling their tickets at more than $2 above face value. Residents in other states are required to follow the same rules if they are selling to Massachusetts residents.
The eBay website also issues a warning: ''Sellers misrepresenting the face value of their tickets may have their listing ended, may be permanently suspended from eBay, and may be subject to criminal prosecution."
Chris Donlay, an eBay spokesman, said the auction site tries to inform its users about the laws in their states and monitor compliance with those laws, but the ultimate responsibility lies with users.
''With 60 million items on the site at any given time, there's a lot of stuff to look at," Donlay said. ''We do the best we can in this very complicated situation, but it's really up to the buyer and seller to comply with the law."
Indeed, a Massachusetts resident last week was selling two tickets for today's game between the New England Patriots and the Miami Dolphins for nearly $170 apiece, well above the $59 face value. The face value of the tickets was not included in the sale item.
There were also a couple of upper-level seats for the Patriots' first playoff game being offered by a Massachusetts resident for roughly $225 apiece. The $75 face value of those tickets was not included in the sale item.
''EBay is great at telling you the rules, but they're terrible at enforcing the rules," said Colman Herman, a Dorchester resident who is working as a consultant to a law firm that is pursuing a class action lawsuit alleging that ticket resellers were violating the antiscalping law in Massachusetts.
Massachusetts officials do not enforce the antiscalping law, and are trying to decide whether to propose legislation that would scrap it or modify it to make enforcement easier.
Bruce Mohl can be reached at email@example.com.