The credit card company knows your billing address, and it is used for verification. For that credit card there is a direct relationship to the billing address.
For some transactions the credit card is not charged until the product is shipped. They will not charge you for the item until a back ordered item is available. You can also pre-order books, movies, computer games to make sure you get an anticipated item in the first wave. In instant transactions the check for a valid card is done during the order process, and a hold is placed on the amount of the purchase. In these delayed transactions they will use the billing info at the time or order fulfillment.
In some business transactions the billing address has zero relationship to the mailing address. The payment could be by credit card (personal or corporate) or by business account or invoice system.
Scenarios where shipping address doesn't equal billing address:
- You live in an apartment, and want a package sent to a place that can accept the box.
- It is a gift and want it sent directly to the recipient.
- It is your kids text books and want it sent to the college campus.
- You are out of town and want it sent to where you are.
- You want to hide it from somebody in your household.
- The student is using the parents credit card.