Are ATMs the perfect machine?
August 15, 2006 12:00 PM   Subscribe

Do ATMs make errors?

I realized the other day that after a more than 15 years of constant ATM use, I've never erroneously received too much or too little money from a cash machine. ATMs break down all the time, and they sometimes run out of money, but I've never heard of a cash machine handing out too much or too little money. My question is twofold: First, have any of you ever received an erroneous withdrawal amount from an ATM? Second, how can these machines operate with such an extremely low error rate? Every other electronic/mechanical device that I can think of -- cars, bicycles, computers, electric grids, airplanes -- break down or make critical or catastrophic errors from time to time. But the cash-dispensing functions in an ATM somehow seem to be immune.
posted by TBoneMcCool to Work & Money (56 answers total)
I haven't, but have a friend who did receive too much (not by much). But (even better) it turned out to be a glitch that the bank couldn't account for, and the entire withdrawal ended up being covered by the bank.
posted by inigo2 at 12:05 PM on August 15, 2006

I got a free £20 from an ATM once. It was taking ages to process, so I hit cancel, and my card was spat out, but then so was the money.
posted by Orange Goblin at 12:07 PM on August 15, 2006 [1 favorite]

I was at an ATM once, withdrawed $40. $60 came out instead. I stared at the cash for a second, trying to comprehend the moral implications of an ATM malfunction and about to decide whether I should feign ignorance and stuff everything in my pocket, when I realized the ATM was talking to me.

"Did you get $20 more?" It said. Great voice synthesis tech, I thought. "Hello?" I asked. "Go to the counter," it said.

I looked sideways, and at a bank counter the teller and a customer was looking at me. A guy emerged from the back of the ATM through a small side door. I gave the complaining customer her lost $20, and left, briefly embarrassed.
posted by suedehead at 12:09 PM on August 15, 2006 [4 favorites]

My mother was at an ATM in Connecticut a decade or so ago and got an extra $20 from it. It was connected to the bank, so she walked inside, spoke to a teller and explained that she had gotten too much money. No one in the bank could figure out what to do, so they told her to keep the extra money.
posted by NotMyselfRightNow at 12:10 PM on August 15, 2006

A friend got $200 when trying to withdraw $20 once. And he didn't even have $200 in the account at the time. Never heard anything from the bank, either.
posted by nixxon at 12:11 PM on August 15, 2006

Best answer: The software end is basically error-proof, to the extent that some of the mainframes will do the same operation twice on two different CPUs, compare the results, & do it again on different ones if they don't match. The code is intensely audited, and rarely, rarely will ever have a problem. Hardware-wise, I'd imagine they get serviced very regularly, and get taken offline at the first sign of trouble. After all, if it gives out a little too much money, that could easily cascade into a lot of money, and that would be a very bad thing for the bank.
posted by devilsbrigade at 12:12 PM on August 15, 2006

Happened to me once ($40 instead of $60, and the bank wouldn't give it back because it happened when they were closed and I didn't have a receipt and they didn't want to check their own files.)
It also happened several times at the bank where I used to work. One bill would get stuck somewhere in the machine and we'd have to fish it out.
When people get more than what they ask for, it's the previous customer's lost banknote.
posted by easternblot at 12:14 PM on August 15, 2006

Best answer: When was the last time you picked up a phone and had it not have a dial tone? Or the last time that you dialed a number correctly but got it connected wrong? (Probably the only way to know that for sure is a programmed dialer or redial.)

Mechanical systems break down, but if my car or bicycle got the maintenance and attention that an ATM does, considering that they sometimes contain many thousands of dollars in hi-use areas, I would expect extremely rare failures. Even airplanes fail at very, very low rates.

How many thousands of flights are there daily? How many thousands of person-miles are driven in a car? And, really think, how many times have you gone to the ATM? If the failure rate is as high as one in a hundred thousand (I would wager it's lower than that), chances you've never encountered a spectacular ATM failure -- and unless you go to the ATM many times daily, you may never experience one in your lifetime.
posted by chimaera at 12:15 PM on August 15, 2006

I was once given $20 too little when making a withdrawal. The bank didn't immediately credit me the $20, either, since the ATM ended up out-of-balance at the end of the day but with too little money rather than too much. As I recall it took a month or two for them to give me the credit.
posted by magicbus at 12:15 PM on August 15, 2006

I had a similar experience as magicbus, except that I received $20 too much. I got a letter from my bank a few weeks later explaining they had tracked down the error to my transaction and were thus deducting $20 from my account (this was circa late 80s).
posted by jamaro at 12:18 PM on August 15, 2006

There are occasionally instances I've read about where ATMs produce the wrong amount of money, not because of a software glitch, but because of human error. Most often, the person restocking the bills in the machine simply puts a stack of bills in a spot intended for bills of a different denomination. This is less likely these days, as most ATMs seem to have been changed over to $20s-only mode.
posted by cerebus19 at 12:21 PM on August 15, 2006

Whoever the guy was that patented the bill-counting gadget used by ATMS must be making a fortune off it.

Never encountered any errors here, but one time, after making my transaction, I was futzing with my backpack and I didn't retrieve the money in time. The machine ate it; the next customer didn't get it. I went to the bank the next morning and they had already found that the ATM had $40 more inside than it should be.
posted by Brian James at 12:23 PM on August 15, 2006

I got an extra $20 once. It was at a free-standing kiosk-type ATM, so there was no bank attached to give it back to.

Why are these errors so rare? Because the machines are designed and built by tecnologically-savvy companies with an inteest in reducing errors to a minimum. Companies like Diebold.
posted by Kirth Gerson at 12:25 PM on August 15, 2006

googling "error rate" & "automated teller" returns some interesting reading.
posted by raedyn at 12:25 PM on August 15, 2006

There was a Washington Post story years ago about an ATM that had 20's stocked into its $5 or $10 hopper, and all the hilarity that ensued, including the eager crowd lined up to use the machine.
posted by NortonDC at 12:26 PM on August 15, 2006

That's probably why so many of them will only give out $20s now.
posted by Kirth Gerson at 12:28 PM on August 15, 2006

I was once given too much money. It may have been that the guy directly infront of me didn't pick up all his cash, I was pretty sure he had though.
posted by robofunk at 12:30 PM on August 15, 2006

Circa 1999, I withdrew $5 from an ATM on campus (poor college students need to eat too) and received two $5 bills instead. I instantly wished I'd withdrawn a larger amount in the hope of a larger windfall, but I figure the 2 bills were just stuck together in the machine and not the result of some magical double-your-money-for-nothing bonanza. To my knowledge the bank never deducted the extra $5 from my account.
posted by junkbox at 12:31 PM on August 15, 2006

Another anecdote for ya...

A friend of mine tried to take out $15 from his bank machine, which did dispense fives. He got three twenties instead of the three fives. Baffled, he checked his balance and sure enough, only $15 had been debited. So, he tried it again and the same result. I'm not sure how many times he repeated, but it kept working until he thought he had better stop, in case he got in trouble.

He never heard anything more about it. Our best guess was that someone loaded the machine wrong, putting $20 in the $5 spot. What employee would want to own up to that mistake?

If this is what happened, it's a case of human error, not a bug in the programming or a breakdown of mechanics.
posted by utsutsu at 12:33 PM on August 15, 2006

I came across an ATM once that seemed to be giving double money to everyone. Unfortunately, I only had like £20 in my account at the time.

When was the last time you picked up a phone and had it not have a dial tone?

This was happening to me for weeks -- they just fixed it. It was completely broken, couldn't dial any number at all. I was a little freaked out, actually.
posted by reklaw at 12:33 PM on August 15, 2006

I went to the bank the next morning and they had already found that the ATM had $40 more inside than it should be.

Most ATMs have a separate compartment into which uncollected money goes, keeping it separate from the rest, thus making it easier to reconcile the transactions.
posted by essexjan at 12:35 PM on August 15, 2006

I received an extra $20 when an extra bill stuck to the ones I was withdrawing. I returned it to the bank, because I'm Lincolnesque.
posted by MegoSteve at 12:35 PM on August 15, 2006

I got shorted by an ATM in New York City many years ago ($20, I think). I went inside to complain, but I had to wait in an insane long line, and it was my only day in the city and I didn't want to spend it in a line, so I sucked it up.
posted by Lucinda at 12:37 PM on August 15, 2006

Response by poster: Based on the anecdotal evidence, I'm beginning to see that my basic assumption is a little flawed. ATMs indeed do fail. It might not be a common occurrence, but it happens often enough that a lot of people have stories to tell.
posted by TBoneMcCool at 12:37 PM on August 15, 2006

posted by Danf at 12:38 PM on August 15, 2006

a bar where a friend of mine once worked had an old atm in it. One night someone stocked it with $100s in the 20s slot. A customer withdrew $20, and got $100 so he took it to the bartender since he was um lincolnesque. So, my friend (more of a Roosevelt) made a free $160 by withdrawing $40 from the machine. The machine ran out of $100s after 2 bills spit out, and then it started spitting the normal 20s. He kept his receipts, talked to the atm guy about it the next day. ATM guy said that there was no way to track it and anyone who stumbled across the $100s was lucky as could be. So no software errors, but magical, wonderful human errors.
posted by ZackTM at 12:52 PM on August 15, 2006

The machine where I work once allowed someone to insert their card and all before it 'realized' it was out of money. He got charged the $1.50 'service fee' for the ATM, but got not money.

I can't help but chuckle at the comment about the quality of Diebold machines, given the track record of their voting machines in past elections.
posted by fogster at 1:00 PM on August 15, 2006

The demonstrated security of ATMs makes the demonstrable insecurity of EVMs all the more baffling/suspicious.
posted by sonofsamiam at 1:02 PM on August 15, 2006

Yet another ATM anecdote: One time, when withdrawing $60 from my account, the ATM decided to play tug of war with the last twenty and ate exactly half of it, leaving me with the other half. It deducted the full amount from my account.

It was just a street level ATM which wasn't connected to a branch, so I had to walk a few blocks down the road to find one to get it straightened out. The manager said they contract some armored car company for all of the servicing, and they didn't have any access themselves. He offered to exchange my half 20 for a full $10 bill, but it would mean taking a loss on the other half, so instead I had them file some sort of loss claim into their system for processing.

To my surprise, a customer service rep called me within the hour, asked me which way the ATM was facing, etc, and located my transaction in the machine's logs. He credited the full $20 back to my account right then. I still have the other half of that bill somewhere; I wonder about cashing it in now and then.
posted by ceribus peribus at 1:12 PM on August 15, 2006

I once had a machine give me $20 instead of $200. It had run out of bills but just kept chugging away, giving me lots of invisible money. It took about 3 months to get it back. I was not happy.
posted by clarkstonian at 1:13 PM on August 15, 2006

fogster, I was being, you know, ironic.
posted by Kirth Gerson at 1:15 PM on August 15, 2006

I used to work at a bank, in London UK, and looked after the ATM's for 10 branches to check for errors. In a twenty four hour period there was an average of 1 error per 10 000 transactions. Basically when the software thinks there has been an error it records the code and then I had to manually check the reciept roll against the account totals to check what the errors were.

About once a week we would have a hungover individual come in and claim the machine gave him too little money when he was out on the town last night! (All such claims I had to check).
posted by ndaguiar at 1:22 PM on August 15, 2006

I've also been charged the service fee after the machine was out of cash. I was (and am still) pissed.
posted by klangklangston at 1:26 PM on August 15, 2006

I tried to withdraw $500 (the daily max) from an ATM the week that I moved to NYC. It gave me an error message on the reciept. I went to another ATM in the same bank (thinking that it was just a glitch), and was told that I had already withdrawn my daily maximum. My account balance was $500 less. This was not my bank, so it took lots of calls and faxing to get things fixed. It took about two weeks to get the money credited back to my account.
posted by kimdog at 1:28 PM on August 15, 2006

I still have the other half of that bill somewhere; I wonder about cashing it in now and then.

Your bill sounds like it can certainly be redeemed for an undamaged one. It's borderline, if it's half a bill, whether it would count as mutilated or not:
posted by jammer at 1:37 PM on August 15, 2006

Response by poster: nakedcodemonkey: I'm referring to transaction errors. As I mentioned in my initial question, I'm well aware that the machines sometimes break down or run out of money. What I was less aware of was how often they dispense incorrect amounts of cash. (and judging from the responses here, it's more often than I thought.)
posted by TBoneMcCool at 1:39 PM on August 15, 2006

Related note: When I was a young lad, this story hit the press, which caused me some wonderment. (Apparently the packet was a flattened Jaffa box)
posted by Kiwi at 1:42 PM on August 15, 2006

I always extract $100, or very occasonally, multiples thereof. Rare indeed has been my experience with an ATM that emitted anything but $20 bills, as I only use my own bank's ATMs (unless I'm abroad).

Once maybe twelve years ago, I requested my usual 5 twenties, but only one emerged, accompanied by four other orange pieces of paper, all blank (and exactly bill-sized). Of course this was after hours. When I went back the next day, they cheerfully swapped my orange blanks for twenties, which apparently mark the bottom of the barrel.
posted by Rash at 1:52 PM on August 15, 2006

Best answer: I work at an ATM software company.

Your question focuses on the Cash Dispenser device. Mechanically, these are complex but basically very reliable. The trade-off for this 24-hr unattended reliability is that they're really expensive. The cash dispenser is one of the most expensive parts of a £30,000 ATM. Certainly, cash dispensers are way more expensive than the PC with Windows XP inside the ATM.

I expect the vast majority of cash dispense errors are human error - i.e. the security guard putting in the wrong cash cassette. The security guard has cash cassettes full of £10 and £20 notes. He puts the ATM into supervisor mode, during which the ATM is unavailable to the public*. He replaces the old, near-empty cassettes with new full ones. They are, generally, clearly labelled "10" or "20". There's a screen on the back of the ATM where he enters the details - e.g. Cassette1 contains 1000 USD $20 notes. I could be wrong, but I think some modern ATMs have the ability to check if the notes they are about to dispense are the correct type by detecting the dimensions of the notes - this is harder with US notes which (correct me if I'm wrong) tend to be all the same size.

Also, every transaction is journalled, either electronically or on a paper printer.

The software end is basically error-proof, to the extent that some of the mainframes will do the same operation twice on two different CPUs, compare the results, & do it again on different ones if they don't match. The code is intensely audited, and rarely, rarely will ever have a problem.

I think this comment must refer to the ATM host at the bank (these are immensely expensive software systems, e.g. BASE24). This is a whole different kettle of fish. Inside each ATM, there certainly aren't two CPUs.

* Note that supervisor mode can't be accessed, on most ATMs, from the front screen.
posted by matthewr at 2:14 PM on August 15, 2006 [3 favorites]

I used to work for a company that provided ATM services for a bank. Indeed there were sometimes errors in the amount of money and there was some settling of accounts to do, but usually it's because of mechanical errors of the hopper. I certainly never heard of a pure transaction error, but I didn't work at the ATM side all that much. Oh and the main reason why they've replaced the small denomination giving ATMs with 20s only ones is that the ATM can then have more money inside, thus necessitating less refills, thus lowering costs. Around here in Finland, ATMs actually give out 20 and 50 euro bills now. And yeah, ATMs have a lot of money inside, they certainly don't want any errors to happen.
posted by insomnus at 2:22 PM on August 15, 2006

One more anecdote.

I tried to withdraw $100 from a vestibule, bank-owned ATM. It made all the right noise, went through the motions, then spat out a reciept and my card, with no money! I immediately called the bank on the hotline phone in the vestibule. They said they'd look into it. I recieved the refund to my account in my next statement, so no harm done.

This is the only problem I've ever had with an ATM and have used them all the time since 1987 or so.
posted by jeff-o-matic at 2:25 PM on August 15, 2006

I have had two experiences with ATM errors. One: withdrew 100 dollars. The machine meant to give me 20s but there was a 100 dollar bill in the 20 pile so I ended up with 180. Two: tried to withdraw (quite a bit of) money at an ATM in Ecuador and received an error saying "transaction could not be completed". Discovered when I got back that the money had been withdrawn from my account anyway. I never saw that money again.
posted by louigi at 3:02 PM on August 15, 2006

Most if not all ATMs have an "audit tape" — an internal paper tape containing a record of each transaction, including how much cash was requested and how much was actually dispensed.

Most of the time, if the wrong amount is dispensed, that discrepancy will show up on the audit tape. When someone at the bank goes over the tape, as they do daily, they will find the discrepancy and correct for it.

In other words, if you get too much cash at an ATM, you'll probably have the same amount of cash taken from your account within the next few days.

In order to keep the excess cash, you'd need the cash dispenser and the audit tape to screw up in the same way, at the same time. And seeing as both parts of the unit are pretty close to foolproof, having the same error in both at the same time is blindingly unlikely.

IAABEBJAT (I am a bank employee, but just a temp)
posted by nebulawindphone at 3:53 PM on August 15, 2006

I once encountered an ATM that dispensed exactly twice as much money as I asked for, while only billing the checking account once. I had, ah... several friends confirm that this happened consistently, it was not a one-off mechanical error.

After a day or so, it went back to normal, and all of our accounts were debited for the full dispensed amount a couple months later.
posted by rkent at 4:00 PM on August 15, 2006

No; like all machines they are infallible.
posted by oxford blue at 4:53 PM on August 15, 2006

1. Most ATMs (these days) count the number of bills that went out and debit you that amount, regardless of what amount you asked for. That's a pretty logical design move.

2. I had a friend go to an ATM late at night to get out $40. He received a $20 and a piece of metal that was labeled "Diebold Money Separator." He was a bit inebriated at the time, and he picked up the courtesy phone and was connected to a customer service person. As I recall he waved the thing in front of the ATM camera and said, "Can't you see me? I'm holding the thing up to the camera!" And he demanded that the person make the ATM eject another $20. Eventually he received a check from the bank for same.
posted by autojack at 4:56 PM on August 15, 2006

One time I found a $20 someone missed when they picked up their pile. (The kind of ATM that drops bills one-by-one into a bin, not the kind that spits them all out at once and holds them in the rollers.) So there can be human error too. I got free dinner.

While eating dinner (this was a place at the pizza joint level of fanciness) someone left their liquor store bag with a bottle of expensive vodka below their stool. I was eyeing it, but they came back in and got it before enough time passed that it was abandoned. So I didn't get free drinks with my dinner.
posted by TheOnlyCoolTim at 5:13 PM on August 15, 2006

I had the exact same thing happen in Jersey City as kimdog- but with 100 dollars rather than 500, and I also thought it was a glitch and went to another ATM. I didn't realize I'd been shorted a full 100 (it didn't even spit out one 20) until later the next day. My own bank was a credit union in another state, and although I pursued the matter I never got my money back.
posted by stagewhisper at 5:36 PM on August 15, 2006

I once did the "withdraw 15, get 60" thing, which was a glory unto my callow college poverty (I think I frittered the extra money away on beer and a Leman Russ - shut up).

A few months later, the extra 45 bucks was charged to my account as the bank noticed the error. Of course, they did this while I had 20 bucks in my account after paying rent and then charged another 40 bucks in overdraft fees. Gah. Unthinking processes, theys works a'fore ya and a'gin ya.
posted by robocop is bleeding at 5:59 PM on August 15, 2006

Around a year ago I attempted to withdraw $100.00 from an ATM machine in a supermarket. Everything went normally except that the machine did not dispense any money. I did get my money eventually but it took a while and my experience dealing with my bank, which owned the ATM, were frustrating enough that I took the account balance down to $0.10 and let it stay there.
posted by rdr at 6:40 PM on August 15, 2006

I did very well out of an ATM about 10 years ago.

I was a customer of bank `A'. I went to withdraw $100.00 from bank B's ATM. The machine spat out $60.00, the third note being crumpled, and stopped. After a long pause it spat out my card. No receipt.

Worrying that I had been short changed $40.00, I went to bank A, to discuss what had happened. They checked their records and said they had no record at all of the transaction. It simply wasn't listed as occurring.

The manager of Bank A said `If was at bank B I'd be moving heaven and earth to find it. Keep the money in your account because they might remove it, but if they don't, it's yours'. Bank B never deducted it from my account.

So, the machine spits out money, doesn't record the transaction at all, and I walk away with $60.00. It still makes me smile.
posted by tomble at 6:42 PM on August 15, 2006

Best answer: Several years ago I worked for an armored car company. My job was to restock atms with cash, make sure they were working properly, and balance them. Balancing simply meant making sure that what was withdrawn during a certain period could be reckoned with what remained in the machine.

The atms were monitored closely. Busy machines on my route I visited daily. Also there were technicians on call who made repairs and sometimes ran their own tests in addition to the ones I ran. And finally, banks have their atms monitored by computer. If something appeared screwy they would notify us and we would take care of it. Like devilsbrigade said above the machines are watched and serviced regularly.

That being said, sometimes their were malfunctions. Mostly from the cash not dispensing properly from the cassettes it is stored in. Also sometimes some of the atms went on a card eating spree. Put your card in and your not getting your card back.

Biggest screw up while I was working there. I and a partner would leave in the morning with the money we would need to restock however many atms were scheduled for restocking. This could be anywhere from a quarter million to a million and a half. I could not carry more than a million and a half since i was driving an armored van. company policy. If I needed more I would have to return to our vault and get more. Anyway, I would receive the money, from our cashroom, for a particular machine in a sealed clear plastic bag ( typically we would leave with 20 or so bags). I would enter a machine and open the safe and pull the cassettes. I would open the cassettes, pull the remaining cash, then put it into a new plastic bag. then break open the bag with the new money and insert it into the cassettes. the old money goes back to the cash room at the end of the day.

However, I had 2 machines on my route that were from a bank we didn't do much business with. They required in their contract with us that their money had to be in sealed cassettes when it left our cash vault. So in that case i would just pull the old cassettes and then put in the new ones. The old cassettes i would take back at the end of the day.

So one day I restocked both atms ( they were located in a busy mall ). 4 hours later i get an emergency call to head to these two machines immediately. Seems that our cashroom stocked the $10 cassettes with twenties. People picked up on this quickly and word spread. Their were alot of transactions during that four hours. Since I could not see inside a sealed cassette, I had no idea what i was putting into the machine. It could have been monopoly for all i knew. These 2 machines were the only ones that had 10 dollar cassettes. All the others were twenties. By the way the bank tried to track down everyone who had made a withdrawal during that time period.

Sorry about the wordiness. In addition to answering your question I thought I might share a little of my experience just for interest and infos sake.
posted by TrolleyOffTheTracks at 8:56 PM on August 15, 2006

"you are" not "your". sorry
posted by TrolleyOffTheTracks at 8:59 PM on August 15, 2006

Seconding autojack's point #1. Many modern ATMs have bill-counters at the exit slot to report how many bills they've actually dispensed in a transaction

A few years ago I withdrew $60 and only got $40. I was about to complain when I noticed that my reciept indicated that only $40 had been withdrawn. I pulled another $20 in a new transaction and got on with my day.
posted by ThePants at 6:22 AM on August 16, 2006

A cash machine went screwy near my old house about three years ago. There was a queue around the block of people taking out twice the actual amount requested. It only ended when the machine finally ran out of money at about 3am. I, as a man of honour, did not draw any money out*.

*i.e. the queue was way too long.
posted by longbaugh at 11:56 AM on August 16, 2006

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