I've noticed recently that several places where I paid with a $20 bill, the cashiers used a small marker to detect whether the bill was counterfeit or not before accepting it. Like so:

I saw this happen at

  • the post office (multiple times)
  • the movie theater

My question is .. why?

I could understand a bank doing this, since it's their job to be strict, but at common salt of the earth places like the movies and the post office?

It seems to me that counterfeit 20 dollar bills should be incredibly rare. But if a bunch of common places check for them .. that implies they must be appearing with some regularity?

Are counterfeit 20 dollar bills (or, is counterfeit money in general) really that common in circulation?

  • Technically, your fake bill above wouldn't pass the test of counterfeiting, anyway. You're not even pretending that it's real money, and no reasonable person would mistake it for such.
    – mbhunter
    Commented Sep 25, 2010 at 8:27
  • 2
    Hmm... I was thinking those detector pens didn't actually work - but when I googled it, I found How does a Counterfeit Detector Pen work?. It's mainly for checking that a bill isn't from photocopier paper, the ink reacts differently with wood-based paper (in real dollar bills).
    – Cyclops
    Commented Sep 25, 2010 at 17:20
  • The only fake money I've received (that I'm aware of) came directly from the bank. A bank named after a prominent country, in fact.
    – James
    Commented Sep 26, 2010 at 2:38
  • FYI, In the UK, fake £1 coins are VERY common.... Have you ever tried to spend any of those Unicorn bills yet?
    – wilhil
    Commented Jun 3, 2011 at 10:50
  • This is an ounce of prevention... After all if a business gave you a counterfeit bill in change how forgiving are you going to be?
    – user4127
    Commented Jul 10, 2012 at 20:00

5 Answers 5


According to this study put out this year by Judson and Porter, the face value of counterfeit currency relative to the total amount in circulation is about 0.01%:

We conclude that the total value of counterfeits in circulation at any moment is on the order of $60 to $80 million, or less than $1 for every $10,000 outstanding, and is highly unlikely to exceed $220 million, or less than $3 for every $10,000 in circulation. Further, we conclude that the incidence of counterfeits is roughly the same inside and outside the United States ...

Actual numbers from five years ago suggest about the same:

Out of the approximately $759 billion in U.S. dollars held in U.S. currency in the form of banknotes (paper currency) in circulation outside the U.S. Treasury and the Federal Reserve at the end of 2005, the Secret Service reported that about $61 million in counterfeit currency was passed on the public worldwide. Of the counterfeit currency passed, the majority, $56.2 million, was passed in the United States, with the remainder passed abroad.

As to why they're checking: Would you want to receive a counterfeit bill?

Costco checks my cash when I check out. The guy I got a buggy ride from up in upstate New York checked my bill. It's easy to check certain things on the bill. Why not?

  • 11
    It's quite a bit more likely than "lottery odds," especially if you accept bills every day. After you've accepted 5,000 of them, there's about a 40% chance that at least one of them will have been counterfeit (assuming "independent bills"). Costco may accept thousands of bills in one day. And the post office? Well, if they catch someone handing them a fake bill, the next thing they do is peer behind to the FBI poster to see if the person handing them the bill is on it.
    – mbhunter
    Commented Sep 25, 2010 at 8:25
  • 2
    @jeff Actually, it's 1 in every ten thousand dollars, or 1 in every 500 twenty dollar bills. So if it costs less than 4 cents to check each twenty, you come out ahead by checking them. That is assuming your bank will catch every fake twenty.
    – KeithB
    Commented Sep 25, 2010 at 18:02
  • 10
    @KeithB Actually, no, it's one dollar out of every ten thousand dollars. Likewise, it's one $20 bill out of every ten thousand $20 bills. It's 0.01%, not 0.2%.
    – mbhunter
    Commented Sep 25, 2010 at 23:10
  • 5
    @JeffAtwood I think you have to keep in mind as well that criminals trying to launder their counterfeit money will probably try to do so via lots of small-impact purchases at retail places. So while there is not that much counterfeit money floating around, there might be certain places where they are a lot more common than in others. (i.e. don't necessarily assume a uniform probability distribution)
    – wds
    Commented Jun 3, 2011 at 10:47
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    @mbhunter - Re "likewise": you're assuming that the distribution of counterfeit bills matches the distribution of regular bills. I'm not sure to what extent that's actually the case. Personally I'd expect to see a lot of counterfeit $20s (a common mid-value bill) and $100s (a reasonably common high-value bill, especially outside the US) and probably not as much elsewhere. I'd suspect $20s and $100s probably have a higher concentration of counterfeits than $50s, $10s, $5s, $2s, and $1s. (I <3 $2 bills :)
    – user296
    Commented Jun 7, 2011 at 19:52

In the few places I worked in my younger years, the establishment lost the value of the counterfeit note when they attempted to pay it in at the bank - they simply won't honour the note.

I remember working a New Years Eve one night and we had taken a few hundred pounds in fake twenty pound notes. The staff were given a strong telling off, because these note were effectively useless and it was up to the staff to check that the notes were genuine.

  • what year was this? I know at least in the USA they've changed the bills a lot to foil casual counterfeiting possible with advanced digital printers, etc -- still happening! secretservice.gov/money_technologies.shtml Commented Jun 3, 2011 at 9:30
  • 1
    Hey Jeff, this would have been around the year 2000. The particular town I worked at the time was having an issue with counterfeits too. If you held a genuine note next to the counterfeit one, without very careful inspection, you simply could not tell which was the genuine. In a busy nightclub on a NYE, this type of inspection wasn't possible - so is it any wonder we were flooded with the things...?!
    – dooburt
    Commented Jun 8, 2011 at 14:56

I imagine that they check it because if they accept one from you and then their bank discovers it when they try to pay it in, it's their loss.

  • 1
    This is incorrect, at least in some countries (not sure about the states). Commented Nov 8, 2010 at 23:22
  • 8
    I'd be very surprised if any country in the world honours counterfeit currency.
    – gkrogers
    Commented Nov 12, 2010 at 15:33

This is supposed to be a comment, as this is anecdotal, but I can't post comments. Also, this information relates to the UK. I used to work in a Licensed Betting Office, or a bookies to use the informal word for it, and we had to deal with this issue all the time.

The pens didn't really work all that well as the forgers found out that dipping forged notes in fabric softener nullified the effects of the pens, and some of the copies were incredibly good.

Generally, we would take two or three notes per week.

  • same comment as dooburt, above: what year was this? They've been changing the bills rapidly in the USA, adding harder to copy features over time. en.wikipedia.org/wiki/… Commented Jun 3, 2011 at 9:33
  • I'm guessing a bookies would see a higher proportion of counterfeit bills than most places. Laundering money by placing lots of bets and then collecting a nearly-equal amount of winnings is an old trick. Commented Jun 3, 2011 at 13:49
  • I worked in the bookies in 2010 and only left in December past, so this is fairly recent. Most of the time fake notes didn't get through as there are fairly straightforward ways of telling the difference in fake notes. The most common fake note was the Bank of England £20. I worked in a William Hill in Glasgow, Scotland. For those of you who don't know, although we use the same currency as the rest of the UK, we have our own Scottish bank notes that are allegedly more difficult to forge. Commented Jun 5, 2011 at 14:21
  • I'd second Jamie's comment about the £20. All the forged notes we took on that night in 2000 were the £20 note. They were however the older Edward Elgar note: uk.reuters.com/resources/r/…
    – dooburt
    Commented Jun 8, 2011 at 14:58

The counterfeit bills that are most popular near my school take a 1 dollar bill, wash the ink off, and print a 20 dollar bill image onto it. A pen cannot detect these. If you have a good printer, you can go from 10 one dollar bills to 10 twenty dollar bills in a day. Mostly teens do this, so 200 dollars is a lot of money. Also, the paper keeps all security feature except for the metallic ink, so the bills don't work at a bank. a guy I know makes money, turns it into bitcoin, transfers it to a zcash account, and then to another zcash account. the money becomes untracable.

  • Do these teens know that they are committing a crime which could put them in prison for up to 20 years?
    – Philipp
    Commented Mar 8, 2017 at 13:40
  • yeah... but they probably don't care. I mean, free money is very lucrative.
    – rohin
    Commented May 30, 2017 at 21:40

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