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If you change your shipping address, it will ask you to re-authenticate the credit card number.

I'm in Canada and I've had to confirm details on my card. I guess outside US thing.

In the US, you do have to confirm the details on your card when you change your shipping address in Amazon, or you need to make any updates to it (i.e. cvv / exiry date). Otherwise, not so much.

Edit: Oops, just noticed that point was also posted twice in sibling comments. Oh well, third time's the charm I guess?

I'm from Canada too. The only time I had to confirm my number / CVC was when I changed my delivery address.

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