This is a YMMV promotion since only some Amazon shoppers qualify. This may be a rotating promotion where it is offered to only a percentage of people at a time, or perhaps the offer is determined by their purchase history. I have no idea how they decide it. The current promotion is a $5 bonus if you load/reload $100 or more as an Amazon Gift Card Balance on your account. To find out if you are eligible, you have to be logged on to your Amazon account, and visit the Gift Card Balance reload page.
NOTE this sets up an on-going reload triggered by a specific account low balance. If you don’t want this to continue in the future, you have to turn it off manually (it is easy to do using your Amazon account page).
You can load this with credit and debit cards but also with prepaid gift cards. So if you have random leftovers of various gift cards you got from rebates, work, gifts, friends and family, you can just load them up to your Amazon account instead of trying to remember how much is left on each card.
Strategically a gift card balance is handy to use as a reserve for small purchases, eg mp3 songs, ebooks, TV episodes, apps, low priced items, movie rentals, etc ~ if you don’t want your credit card statement filled up with small amount transactions.
I am not eligible for this iteration of this promotion, so I get this message (annotated screenshot crop):
If you are not logged to an Amazon.com account when you visit that page, you will see this message (annotated screenshot crop):
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