Not really a help request, just a general query, I made a purchase via my Kindle about an hour ago, 1st one I’ve made in a while to be fair, how long does Amazon actually take to bill you for the purchase 
Books downloaded on my Kindle and the purchase history confirms it’s been bought, I’ve had no email confirmation as yet and nothings been charged to my account.
It’s my Monzo account showing on Amazon and no other associated cards so I can’t have chosen the wrong one in error.
My kindle purchases usually come through around 3 - 4 hours later 
Oh that’s ok then, when I didn’t get the notification about spending on my card I went to double check I’d not got a different card registered 🤦🤣
I’ll know for next time, weird way of operating you’d expect payment to come out in an instant given its a digital download an all
Might be to give you a chance to refund the purchase easier. I believe they give you the option to refund immediately on the payment page for accidents etc. But that’s just speculation. I imagine it’s something more technical and/or mundane lol.
I did think about accidental orders but I’ve just checked the order page for that and you have a 14 day window to claim a refund for a book you’ve accidently purchased, so think it’s more likely to fall into the mundane category 🤷
Still not had the payment go through at present, the clocks still ticking 
You’re not carrying a Gift Card balance are you?
I had the same when I bought Amazon Coins last week and, somehow, it reverted back to the Gift Card balance, despite me repeatedly changing default to my card.
Hence, no kerching!
It went out at 0230 so a fair few hours after purchasing it