US currency serial numbers and Counterfeit question

I am writing a short sci-fi story about a man who moves through parallel universes. I realized that he might run into an issue spending cash from one universe in another. If he spent a large amount of cash in one world, that came from another, would it cause all kinds of alarms to go off at the Federal Reserve? Depending on how you look at it, the money is real US currency, but still ‘counterfeit’ in that it’s either going to duplicate already existing serial numbers, or have unreal numbers. My suspicion, and how I’ve written it so far, has no alarms going off until the Fed destroys some bills and records their SN’s as destroyed, then gets duplicate SN’s showing up later. The idea of the existence of multiverse travel being exposed by something so mundane amuses me.
Thoughts? Opinions?

It’s unlikely that any alarm would ever go off. Banks do not have a process in place whereby the serial numbers of banknotes are routinely scanned and compared against a database of existing (i.e., issued) serial numbers, or a database of serial numbers of banknotes stored elsewhere. Banks do have processes in place to check the authenticity of banknotes that are paid in, but in your scenario the banknotes would be detected as genuine because they have all the security features built into genuine banknotes. The serial numbers are not scanned and tracked as a matter of course.

Another matter, of course, is whether an alarm would go off once the banknote is removed from circulation and destroyed by the Federal Reserve. Whether that would set off an alarm in your scenario I’m not sure. I used to work at Deutsche Bundesbank, which issues euro banknotes in Germany and puts them into circulation (and also removes them from circulation); and while I was not involved in cash handling myself I knew people who were and I have seen the facilities where this takes place. My understanding was that even at that point, the serial numbers of the notes are not scanned and run across a database. The amounts of banknotes destroyed is, of course, recorded, but to my knowledge these records are not as granular to capture the individual serial numbers. I might be wrong, though, and I couldn’t speak for the practices of the Federal Reserve.

If he’s using one dollar bills, he might puzzle some people at Where’s George. That site could be used for an interesting subplot involving someone trying to figure out the nature of this oddity.

How many bills would he have to introduce into circulation to the point where two bills with the same serial number could appear often enough for someone to notice, even without the bills?

Also, isn’t there a thing they sometimes do where they use bills with a specific serial number to set up a sting? Could that be the issue instead–that he just happened to have a bill that was part of a sting in our world?

Though I do like the idea of Where’s George cluing people in. It would be nice if it’s the lowly $1 which no one thinks about that unravels the whole thing.

Actually, the WG site will track any denomination, $1 to $100. It’s just that dollar bills are by far the most often entered. I’ve been a Georger for years and my percentages are:
71% $1
26% $5
3% everything else, most of those 20s

Having a dollar bill unravel a nefarious plot would be an interesting plot point, rather like germs bringing down the invasion in War of the Worlds.

That was what I wasn’t sure about: Would the fed even notice? I’ve worked with inventory tracking systems that don’t bat a digital eyebrow at duplicate items, and ones that flip out from them. I probably don’t want to rely on that for a major plot point if I don’t know.

It’s funny you mentioned that. I came across that site in my research, and it was in fact a post on this site that brought me here, and inspired me to create an account. It’s going to be bills of all denominations. Basically the guy’s plan is to trade back and forth across universes. Agave goes extinct in one world, import top shelf tequila from another and sell it for thousands of dollars. Pharma Bro jacks up the price of a medication in one world, guy brings more supply from another. Those sorts of things. He would be flush with cash, but wouldn’t bother to keep track of what universe any particular chunk of cash came from, and a silly SN would bring him down.

I think you nailed a solution. Rather than leave a plot point in the air and wing it, or risk getting on some watch list for investigating it, I can just do the sting thing. Guy get’s caught spending a $100 bill that in this universe was in a bank’s bait drawer when it was stolen. They nail him for the robbery… until an identical 100 pops up. I like it…

I always thought multiple universe import/export trade was perfectly legal. No counterfeiting involved, although usually it’s easier and they prefer it if you just use an electronic funds transfer. (Who hauls around bales of cash?)


When he moves into a new universe and wants to buy something, but has nothing to sell there yet, what’s he gonna do, get a day job? Also, it’s hard to get a bank account somewhere where you don’t technically exist, and I don’t want to start researching fake identifications. I’m sure my search history is already pretty ‘interesting’.