ELI5: Why do card payments stay 'pending' for days after the money leaves an account?

Card payments stay pending because your bank hides the money so you do not spend it twice, while the store takes a few days to actually collect the cash.

Think of it like putting a toy on hold at a toy store.

When you swipe your card at a shop to buy a five-dollar ice cream, two things happen at different times: the promise, and the actual delivery.

• The Promise (Authorization): The store asks your bank, "Does this person have five dollars?" Your bank says yes, immediately sets that money aside in a little private box, and marks it as pending. You cannot spend that money on anything else, which makes it look like it is already gone from your account. But your bank has not handed the dollars to the store yet.
• The Delivery (Settlement): The ice cream shop does not run to the bank every single time one person buys a cone. Instead, they collect thousands of receipts all day long. At the end of the day, or sometimes over the weekend, the shop sends this giant pile of receipts to their bank in a big batch.

Once the cash actually travels to the store, your bank changes the label from pending to posted or cleared.

This process often takes two to three business days because banks are closed on weekends and holidays, and millions of receipts must be safely sorted and traded behind the scenes. In short, the money vanished from your view instantly, but it is just waiting in the hallway until the store officially asks to take it home.