Found this on another site when somebody asked about pre-orders and charging straight away...
Thank you for your patience, our billing team have come back to me with the following information.
We're introducing some improvements to payments and authorisations in order to simplify your shopping experience on Amazon.
When you pre-order an item that is yet to be released, we charge you the full order amount when the item gets dispatched. If the shipping date is set after more than five days, that charge occurs on the fifth day since your order was placed.
We’ll dispatch your item as soon as it gets released. You can check updates to your order status, or cancel your order anytime before it gets dispatched, by visiting Your Orders at amazon.co.uk/you…ers.
Whenever you pre-order a book, CD, video, DVD, video game or software item from Amazon, the price you pay will be the lowest price offered by Amazon.co.uk between the time you place your order up to and including the end of the day of the release date. If your order qualifies for the Pre-Order Price Guarantee, you'll be refunded the price difference once your order dispatches.
I hope this helps. We look forward to seeing you again soon.”
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So in other words, preorders and out of stock items will be charged on the 5th day after placing an order, regardless of the dispatch date.
Amazon have given different replies to customers
This is another reply amazon have given
Hello,
We're introducing some improvements to payments and authorisations in order to simplify your shopping experience on Amazon.
When you pre-order an item that is yet to be released, we charge you the full order amount when the item gets dispatched.
If the shipping date is set after more than five days, that charge occurs on the fifth day since your order was placed.
We’ll dispatch your item as soon as it gets released. You can check updates to your order status, or cancel your order anytime before it gets dispatched, by visiting Your Orders at Amazon Sign In .
Whenever you pre-order a book, CD, video, DVD, video game or software item from Amazon, the price you pay will be the lowest price offered by Amazon.co.uk between the time you place your order up to and including the end of the day of the release date. If your order qualifies for the Pre-Order Price Guarantee, you'll be refunded the price difference once your order dispatches.
Immediately after you place an order, we now request your bank to authorise the full order amount. At this stage you’re not being charged yet – your bank is reserving the funds until the transaction processes.
We only charge the full order amount when all the items included in your order have been shipped.
Should an item require more than 5 days for dispatching, your payment method is charged on the fifth day since your order was placed.
This new experience will avoid processing multiple authorisations and charges for the same order.
I hope this helps. We look forward to seeing you again soon.
Warmest regards,
Jem G.
The above amazon reply contradicts itself
1)We charge you the full order amount when the item gets dispatched
2)We now request your bank to authorise the full order amount. At this stage you’re not being charged yet – your bank is reserving the funds until the transaction processes.
3)We only charge the full order amount when all the items included in your order have been shipped