It is only available in City Folk and is only useful at GracieGrace and the Auction House, because the prices can be extremely high and only 99,999 Bells can be carried at a time. The player may only get the Shopping Card by depositing over 10,000 Bells into the Automatic Bell Dispenser (ABD). A letter will be received with the shopping card attached the next day. However, since it won't work at Tom Nooks, nobody can use it there.
Gold Shopping Card
To obtain the golden card, the player must have 1,000,000 Bells deposited in the ABD and it works the same way as the basic shopping card, except it gives a 20% discount on every item in the store.
Lost Shopping Card
If the player loses their Shopping Card, they are able to go to the Automatic Bell Dispenser and select "Reissue Card". They will receive a new card in the mail.