I noticed that eBay and Amazon do not display billing address in order summary once the order has been processed.
Does this mean that billing address is not relevant information for the user once the order is done?
If the billing address is the same as the shipping address, there is not much reason to show it for consumer purchases. If they are different, then one could make a justification for including it, but I doubt a customer would really desire it.
For business-to-business purchases I would suggest including the billing address if it is different, and possibly always including it. just ensure that the shipping address is more prominent, and the two are clearly labeled. Some companies have several of each address, so the inclusion can be useful.
Why would billing address be relevant if the order is complete? The purpose of a billing address is to verify ownership of the bank card when submitting payment.
Also - they display the shipping address. Displaying both shipping and order address on the same screen leaves too much room for confusion.
Billing address typically is used to verify payment. If the payment is already verified, then presumably there is no reason to send that billing address to the user in a confirmation e-mail
Billing address is sometimes needed for extra security, apparently. Although I have no idea why when the CSV and other card details are built precisely for this. I suppose Amazon know this.
Another answer is that billing address will likely be same as home address in which case it is redundant.
Billing address seems to be a carry over from business accounts and has no place in normal transactions. Don't believe me? Try filling out dummy data in your next transaction over the billing address fields and see if it processes. Answer: it does.