Consumers could be burned by a hidden tip at many restaurants if paying with some gift cards. It happened to a Volusia County man who called WFTV's Todd Ulrich for answers.

At an Outback restaurant in Sanford, John Konkel claims his 20 percent almost turned into a 40 percent tip, and he blamed a Visa gift card.

“I just wanted an explanation. Who was responsible?” asked Konkel.

The receipt shows Konkel's dinner cost $34. He paid with a $50 Visa gift card as he was leaving a 20 percent cash tip. But then he checked the gift card receipt left by the server, and the card balance showed Konkel was already charged an extra $6 and some change, which came out to roughly a 20 percent tip.

>> Read more trending stories  

“Did you tell the server to deduct 20 percent from your gift card?” asked Ulrich.

“(I) did not. As a matter of fact, I had the money out since I leave cash tips,” said Konkel.

When he asked restaurant managers why, “The manager said it was 100 percent Visa's problem, that they dictated the policy.”

When processing systems pre-authorize an extra 20 percent from credit card-branded gift cards at many restaurants, it's called Tip Tolerance. If you leave less or no tip, the balance is returned to the card.

But many consumer groups said customers aren't told and that the practice is confusing and can turn into unauthorized fees.

"In this particular case, it's a big deal, and you want to make sure you know exactly what you're paying," said Matt Shultz with CreditCards.com.

Visa's corporate office told Ulrich restaurants or processors enter the preauthorized tips, not Visa.

Outback said it was not responsible and blamed the tip hold on the bank that issued the Visa card.

Konkel said unless he carefully checked receipts, “There was nothing there to say they had taken out a tip.”

After complaining, Konkel only left a 20 percent tip.

Ulrich found many online complaints involving credit card-branded gift cards at many different restaurants.