All these are good for are voice authorizations. They're typically used when the CC machine returns a code like "Call Center" or when the machine is down altogether. In the first case, they'd try to put the transaction through manually and then tell you that you need to take the card, keep the customer there while they call the police because it's stolen, tell the customer it's denied, etc. For voice authorizations, they take the card number and the amount and issue an authorization number like the CC machines do. I believe this just places a hold on the account for the amount authorized. Typically the numbers are entered into the POS and the system later sends the authorization numbers back to the CC servers to turn into sales. You could probably request this by voice, too, although I've never had to do this. Things could be different now as I haven't worked in retail for over a decade.... If you do this, you could at least max out someone's card temporarily until the authorization comes off. If you managed to turn it into a sale then the money goes into the account tied to the Merchant ID. Of course it probably wouldn't stay there for long and get charged back. If you try to do it for any serious amount of money they could want to speak with the customer and verify some account details before they put it through.