@BronzeTrader wrote:It seems most of the UA cards have the same card numbers and CVV codes with the master CCs. If so, nobody can tell if the UA card is used electronically. Maybe there is still some difference inside the magnetic strips, so the CC companies can still tell?
I can't speak to if the magnetic strip has different data that is significant to the issuers, although since some places print your name on the receipt I would assume that at least that much is different for the authorized user (AU); i.e. that the name printed on the receipt would always match the name embossed on the card, even if the card number is the same as the primary account holder, or else the merchant would suspect a skimmed card.
I have an AU for my Chase card and my Quicksilver Visa. For Chase, the card number, expiration, and CVV are identical to my card, however with Capital One all of the information is different. My Capital One statement is actually very convenient, since it breaks-out my AU's charges separately.
With Capital One I also see the AU card separately on my 'Wallet' app, and if one card is temporarily lost I can even "turn it off" without impacting the other card (even on the same account).
I don't know how other issuers handle this (same number vs. different number)... I'll leave that for others to chime in on. 
