In California the cashier can no longer ask for your zip code during a purchase. But even if this isn’t the law in your state, you should know if they do ask, you don’t have to answer.

Last week California’s Supreme Court ruled that asking for a zip code infringes upon consumer rights. The Song-Beverly Credit Card Act of 1971 prohibits stores from recording a consumer’s “personal identification information” during credit transactions – and the ruling labeled a zip code as personal information. Since the ruling, consumers have filed class action suits against major retailers in California, including Target, Wal-Mart and Victoria’s Secret. The penalty for requesting such information can be anywhere between a penny and $1,000.

Matt Valdes, senior associate attorney at Kaufmann Englett & Lynd Attorneys in Orlando, Fla., said nearly a dozen states already have laws in place against recording consumers’ personal information, like zip codes, and the ruling may prompt these states to reevaluate their own policies. Credit card companies like MasterCard and Visa also have their own rules about such information.

“This will open up the door for similar actions in those states,” Valdes said. “This allows zip codes to be considered personal identification information.”

Many consumers have no idea that there is no law stating stores need the zip code to complete credit transactions and they are not obligated to comply with such requests, he said. A retailer can request an ID to complete a credit purchase, but it is illegal to record any information from the ID.

“People just do it uniformly,” Valdes said of giving their zip codes to stores. “People think that they are doing it to confirm it’s their card and protect you, but in reality they are doing it for their own marketing.”

Retailers often run a reverse check on the shopper to obtain their address information, and then proceed to send them marketing information, according to Valdes. These mailing lists are often duplicated and sold to other retailers.

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