Use American Express gift card on Amazon

EDIT for Dec 2023 and beyond:
Trying to do an Amazon Reload for the entire amount minus $0.10 got rejected every time, even using lower increments like $100 or $50.

It appears you can process two $25.00 Amazon Reloads in a 24-hour period.  You must run one and wait for it to get to completion (takes around 5 minutes), then try the next one.

A better idea (kudos to my boss for suggesting it) is to take your AMEX gift card to Walmart and purchase an Amazon Gift Card from them for the same amount.  Then you can run one Amazon Reload transaction for the full amount.

 I ran into a snag trying to load my Amazon gift card balance with prepaid American Express gift cards.  I learned what went wrong and was able to correct it, so I hope this article will help you get it right the first time.

The ideal way to use the gift card is to add it as a payment method in Amazon, then use the "Reload your gift balance" function to convert your Amex gift card to Amazon credit.  Then if you need to make purchases that would be split between your gift card balance and your default payment method, it will go without a hitch.

The caveat at the time of this writing is, when you add the gift card as a payment method, Amazon will validate the card by requesting a $0.10 auth on it with the issuing bank, which will lock that amount, leaving you $0.10 less  than the full amount of the card that you can reload your gift balance with.

That said, if you have a gift card for $100 and you want to use it on Amazon, you're really going to reload your gift balance with $99.90 instead of $100.00

Steps to load your American Express gift card into Amazon:

1. Add your card as a payment option in Amazon
1. Log into Amazon
2. Navigate to Account | Your Payments
3. Click on the "Wallet" tab if not already there.
4. Under the "Cards & accounts" section, click the "Add a payment method" option
5. Under the "Add a New Payment Method" section in the right pane, under "Credit or debit cards", click the "Add a credit or debit card" button.
1. Enter the card information
2. Uncheck the "Set as default payment method" button
3. Click the "Add your card" button
4. Make sure it was successful
2. Verify the hold Amazon placed on your gift card by going to the Amex Gift Card Balance website. NOTE: This can take up to 15 minutes to appear...
1. At time of this writing, my auth hold was $0.10, but your mileage may vary depending on when you attempt it.  If you confirm the amount on the Amex website, you will know how much to deduct from the full amount when reloading your Amazon gift balance.
2. UPDATE 2022-12-09: Amazon didn't apply the $0.10 after 15 minutes of adding the card as a payment option in Amazon.  It waited until I executed step 3 below (purchasing the "Amazon Reload"). I made the mistake of trying the full amount since I hadn't seen the $0.10 hold.  Amazon accepted the purchase, but being suspect, I went back to the Amex Gift Card Balance site and looked at the transactions again. The $0.10 Pending Transaction immediately appeared.  So I get to contact Amazon and tell them to cancel and try again with the $0.10 deducted.  Lame. 
   
   My recommendation is to just proceed to Step 3 and immediately load the balance assuming you won't be able to use the $0.10
3. Reload your gift balance on Amazon
1. Navigate to Account | Your Gift Card Balance
2. Click the "Reload your Balance" button
3. Enter the adjusted amount in the "Enter an amount" textbox (in our example of a $100 gift card with a $0.10 hold, you would enter $99.90)
4. Select the American Express "credit" card under "Your credit and debit cards"
5. Click the orange "Reload $99.90" button
6. You will get the message that the order is being processed and should receive an email a few minutes later confirming that the balance is reloaded.

Amazon will not allow you to edit or cancel a "Reload Your Balance" order, so attempting to load your entire card while the auth hold is in place, will result in your order becoming stuck in a "Payment revision required" loop where Amazon will email you stating the transaction was denied and that it can't be completed unless you revise your payment method.  Revising your payment method means logging in to Amazon and changing which card you're using to reload the balance.  Since you don't want to use a different payment method, you are left to contact Amazon support; who will be tempted to tell you that the hold is at the bank and that you need to contact the bank... or they will mention that you entered the credit card information incorrectly and will need to correct it.

Neither will be true... you simply tried to reload more than what is available on your gift card... so the support agent will be required to cancel the order so you can place it again with the proper amount.  Again, you can discover the proper amount by investigating the auth hold on the Amex Gift Card Balance site... then subtracting that amount from the total of the card.

Happy shopping!