California's civil code prohibits businesses that accept credit-card transactions from printing any more than the last five digits of customers' card numbers on their receipts. The law took effect on Jan. 1, 2001, for any machines installed after that date, and all California machines were required to comply with the law by Jan. 1 of this year.

Joanne McNabb, chief of the state's Office of Privacy Protection, said California is the first state to enact such a law, but similar federal legislation will take effect sometime next year.

She said it is important to print only truncated numbers on receipts, because some people will actually rummage through trash to find entire numbers. Even without an expiration date or name and address information, people can use complete numbers to complete some transactions, or worse.

"For the more organized thief, they can create a new credit card," McNabb said. "Unfortunately, the kind of equipment that you need to create false documents and cards is readily available."

Although many Saratoga business owners said they were aware of the law and made the changes to their receipt printers if necessary, some said their machines still printed the entire number.

MaryAnn Serpa, owner of Skin Prophecy Boutique on Big Basin Way, said she did not know about the law.

"I should get ahold of them and see what I should do," she said, adding that she was surprised her transaction-system provider did not contact her about the change.

But McNabb said neither the providers nor the government is required to notify business owners of the law. Still, most should be aware.

"We've gotten lots of calls from individuals—people are finding out," she said. "Here's who really should be [notifying people]: the companies that produce that equipment. It's not going to be effective for the 4.5 people in our office to notify every business in California."

Most Saratoga business owners said they heard about the law via word of mouth, newspaper articles, or a notice included in the last Chamber of Commerce newsletter.

Mei Huang, owner of Saratoga Bagels on Saratoga-Sunnyvale Road, said she had not yet changed her machine, but just found out about the law and intended to call her credit-card processor soon.

"They should tell us about it," she said. "I found out from a relative."

Though they are not required to do so, some providers are notifying their customers of the law as a courtesy. Pauline Lee, owner of Paperfunalia gift shop on Big Basin, said she was contacted by Nova Information Systems and had her machine changed. She said it was easy to do, and that her customers have been appreciative.

"It's a great thing," Lee said. "The customers love the fact that their whole number isn't printed on their [receipt]. If you lost that, then everybody's got your history, don't they?"

Michelle Graff, Nova's vice president of marketing, said her company has been diligent about asking customers to comply with the new regulations and sent out a letter to notify customers of the change. The company also sent a photo illustration with the letter, showing clients the difference between a truncated number and a full number on a receipt.

Updating the machines is a fairly straightforward process and doesn't take more than a few minutes, Graff said. For most Nova machines, simply upgrading the software can achieve the desired result. Most customers can use their machines to dial Nova and upgrade their machines over that connection.

Some merchants said their machines were already compliant. Patrick Rupert, owner of the Uncorked wine shop on Big Basin, said he would be "very concerned" if some businesses still were not.

"Shop owners need to do whatever they can to protect the personal information of their customers," he said. "I think a lot of it has to do with common sense."

Reporter Nisha Ramachandran contributed to this story.