Won't the system will purge them at month end close.

It's odd, we see some still around months after they expired. Maybe accounting isn't running month-end?

But even if that happened we'd need to display a message to the order-entry person that the credit card order they're entering is for a customer without CC info on file.

So I thought maybe it's enough just to show the credit card info on the header screen. But when I put the expiration date(s) and last 4 unencrypted numbers on that screen they don't show anything and they look grayed out. I'm pulling them from the SO_SalesOrder_bus.EncryptedCreditCardNo area.

I don't need to do anything with this data, I just want to show it to the operator.

Would a script that simply pops up a messagebox stating the credit card is expired work? Thats fairly simple to do.

Yes, that would work. If the card is expired or there is no card on file. In this case, the client is using terms code 07 and 08 to indicate credit card sales, but I suppose any terms with "Credit Card" in the description would future-proof it.

So, if Terms are credit card and there is no credit card info on file or the card (all the cards) on file are expired, they should see a message.