SAN FRANCISCO (CBS SF) — They used to be called cash registers.  Now, they’re known as point-of-sale systems.

The tablets and computers that merchants use to add-up customers’ purchases have been a boon to businesses that  like the additional features they offer,  like inventory tracking and employee payroll.

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But some of the high-tech  systems may be running afoul of an 18-year-old California state law.

California Business and Professions Code 13300a requires businesses to “conspicuously display” to the consumer the price of each good or service as its being rung up. San Francisco gelato store owner Mauro Pislo  told ConsumerWatch he was  recently told by city inspectors his Square payment system didn’t comply with the  law  because it doesn’t have a customer-facing display.

That’s something Pislo says wasn’t made clear to him by Square or the city when he purchased the system.

“Nothing included this feature. Nothing,” Pislo told ConsumerWatch. Pislo says inspectors told him he’d need to come up with a solution.

San Francisco’s Nancy Sarieh says simply flipping the screen to show customers the prices isn’t allowed.

“The law states the consumer needs to see the transactions as they are happening,”  Sarieh explained. “If they’re not showing it to the consumer,  they are not in compliance with the law.”

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San Francisco-based Square told ConsumerWatch: “We recognize and take seriously the need for our sellers to comply with local state and federal laws.” The company says it now offers a software solution to address the issue. It requires companies to use an iPhone as an additional customer-facing screen.

San Francisco contends the compliance rate in the city is high.  According to city records, 93 percent of businesses registered with San Francisco County comply with the state law. But ConsumerWatch found a handful of stores with three blocks of  our station without consumer-facing displays.

County records showed none of those systems are registered.

ConsumerWatch contacted the eight other Bay Area counties about if and how they’re dealing the law and found varying levels of  enforcement.  Several said they consider flipping the screen to show a customer the price an acceptable solution.

Napa County Agricultural Commissioner and Sealer of Weights and Measures Greg Clark said  the law is out of date.

“The law needs, to the extent possible, stay current with technology,” said Clark.

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San Francisco  contends businesses may also comply with the law by posting signs near the cash registers listing the prices of all their items.