Does the ZIP code have to match the billing address? Or are they just collecting demographic information? What happens if you put in 90210?
I apologize for my previous signature.
I still have them turned off.
It's as others have said. An added security measure. If the zip code you put in doesn't match the billing zip code, the transaction is denied. I've had to use it at gas stations at the pump and enter it for some retail stores (like Walmart) when I use my AMEX.
As someone whose business has taken credit cards online--yes, it is for verification purposes. The system we used required the address and zip for the credit card. The numbers in both the billing address and the billing zip code had to be associated with the card number or it was not considered valid. I'm sure some companies do it for demographics, too. But ours was required for transaction approval.