From Binding of Isaac: Rebirth Wiki
The Credit Card is a Special Card.
- Using the Credit Card in a Shop instantly removes the cost of all items in that shop, allowing Isaac to take all of them for free.
- Using the Credit Card in a Devil Room or Black Market allows Isaac to take all the items without any health cost.
- Taking Devil Room items with the Credit Card does not prevent Angel Rooms from appearing.
- Works with the Blank Card, allowing Isaac to purchase all items from every shop, if used correctly.
- Using the Credit Card in a Shop prevents Restock from working in this shop only. However, Restock Boxes will work, creating new items.