A reader named Michael wrote in to tell us about a recent trip to his local Walmart, where he and his wife picked up a pile of groceries totaling over $100. When his wife attempted to pay with her MasterCard at the register, she was asked for a photo ID.

The cashier said that it was store policy to require ID for all credit card purchases over $100. But if, as Michael says, the card was signed on the back, then the store was in violation of MasterCard’s merchant’s agreement by demanding to see ID before completing the transaction.

Alas, Michael’s wife relented and pulled out her license just to get out of there before the food went bad. But, regardless of what a cashier ever tells you, if a credit card is signed on the back, the merchant can not demand photo ID in order to complete the transaction. There are situations where a merchant may require additional information, such as a zip code, for verifying phone/online/mail orders or for shipping purposes. But they don’t need to see your ID in those situations either.

Here is some pretty good information about credit card facts and fictions.

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