Google Wallet shows $1.20Monday night I got a Dr. Pepper from a vending machine. What made this an event for me was this vending machine had Tap and Pay and it actually worked, which is something that’s not been the case with any soda machine I’ve run across for the past two years.

I tapped, got the immediate confirmation of $1.20 paid, status pending (screenshot right), and a transaction ID. An authorization was sent to my American Express card to hold $1.20 (screenshot below). I got an email from Google the next day saying I had successfully charged $1.50, Google Wallet changed the amount listed in the application to $1.50 (screenshot below).

While 30 cents wasn’t going to make or break me, having an authorization amount smaller than the charge amount theoretically could cause issues with overdraft or declined charges.

I wondered what caused this. For a clickbait headline I envisioned “the $125 can of Coke” and a listing of overdraft fees by various banks, but it’s 30 cents, and I try not to clickbait and this just isn’t that interesting.

What appears to be the issue is that with vending machines is your card is pre-authed for the amount of the most expensive item in the vending machine, and later it’s charged the generally lower amount that whatever item you purchased was, this according to the $5 Candy Bar. Sort of like when you use a card at a gas pump your card has a temp hold of the mythical maximum amount.

Google Wallet charge difference

In this vending machine’s case the highest amount had most likely been set at $1.20 back when the machine had that as a maximum. Everything was $1.50 when I hit it. Pre-authed for the 2014 top-end $1.20, charged the 2015 $1.50, and then Google Wallet updated in the background.

Google Wallet weirdness at 150This might become an issue if you’ve got the back end funded with a debit card and you’re dealing with a vending machine that includes Dr. Pepper, Aquafina, and $600 bottles of wine, however that’s probably not something you’re going to run across often.

The issue does not appear to be limited to Google Wallet, it’s any credit-card accepting vending machine. It’s just with Google Wallet I got to watch as the price changed and got screenshots along the way.

So in the end, this was most likely a vending machine configuration issue that was revealed by Google Wallet.