I’ve written before about problems with the UI on ATMs, such as repeatedly asking what language you want and having you enter cents for withdrawals when no ATM I know of dispenses pennies.

I ran across another problem the other day: an ATM that doesn’t know when to count. I asked for $200. The machine connected to the network, subtracted $201.85 from my account and then started spitting out money. Whirr. Click. Uh oh.

Seeing as I wasn’t in Vegas and there is no such thing as a $200 bill, I began to worry. There was an ominous message that said simply “Cash dispensing error”. The machine only had $20 in it.

The machine should keep track of how much it has in it so that as soon as you enter $200, it checks and says, “Sorry, I’ve only got $20. Do you want that?” This should happen before taking the money out of your bank account.

Here’s a case where bad UI made the ATM company money: I ended up paying $1.85 to withdraw $20, a whopping 9.25%. If I’d known that there was only $20 in the thing, I would have used a different ATM. Now if only I’d reprogrammed that ATM to think I took out $5.