Do you get interest charges on Pre-authorization hold on Credit Card?

Question

Lets say I ordered an Item from amazon using a credit card for $100 The merchant cancels the transaction for whatever reason, before the item is shipped.

Amazon states that they do not make any charges to your account if the order was cancelled before it was shipped. The bank will do a "Pre-authorization charge" to test if you really have $100 on your card. There is no money transferred to the vendor, but your bank just allocating $100 for the transaction.

While the Pre-authorization charge is in effect, will this amount ($100) also be reflected on your credit card's due date or will it be excluded? especially when you've gone past the billing cycle of your credit card. If it is included, are you also charged interest for it?

Also how many days does it take for a pre-authorization charge fall off in credit cards? Will using debit cards result in faster times for pre-authorization charges to fall off?

Answer 1

Pre-authorizations (same as not-yet-completed transactions) do normally not go onto your bill, do not generate or trigger interest charges, and are not 'due' to pay at any time. They do reduce available spend - they count towards the maximum allowed on the card.

Note though that when a pending transaction or preauthorization becomes a complete charge, they can become so retroactively to the date they were initially made. If your bill is already closed, that has no impact, but if your bill closes afterwards, they are on the bill now. If you are paying interest, the interest will also become retroactively calculated.
I have seen this happening more than two weeks backwards (pending charge on the 5th, became a complete charge on the 20th, carrying the date of the 5th).