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Comment by O__________O | Hacker News Reader

My understanding is that much like tracing blockchain transactions, cash is much easier to trace for governments than most people realize.

For example, it is my understanding, most banks and ATMs scan serial numbers when receiving or distributing cash; oddly, banks will not give you itemized list of serial numbers of the bills they distributed, which would be useful in cash seizures. Also my understanding that most cash withdrawals are spent with vendor that deposits the larger bills back on receipt and do not recycle them back into circulation. As such, not sure what percentage of cash transactions are traceable, but not an insignificant percentage and per person, given largest enough cash flow, would be very hard to stay anonymous; which is not even account for tracing asset flows themselves related to the transactions.

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> most banks and ATMs scan serial numbers when receiving or distributing cash

That is potentially a clue. But in itself would not answer to a legal certainty (that one fact) that a bill with a serial number in a nefarious transaction means the person who withdrew it (from the ATM) made the transaction.

1) I can withdraw $300 from an ATM and purchase a coffee (using $5 of that). That $5 might be refunded as change to someone who then uses it (to buy chinese food) and then as change to another person. And that person purchases something that they shouldn't.

2) Of course at scale with large amounts (say $300 withdrawn 10 times to equal $3000) used in a nefarious transaction yes they could trace back but they still wouldn't have proof that the person withdrawing it didn't pass it to someone else (who then used it). Further they can't require you (in the US) to disclose what you did with the money after you withdrew it. However they might try to convince you you have to answer and tell them.

3) That said of course like with anything again yes it would point them in some way to you and then might be able to find another way to then focus on you and get what they need (in order to get a warrant to do a search or get other records released).

You’re expanding way beyond what’s necessary to track significant amount of cash transactions; also, not claiming 100% of transactions are able to be tracked, just that significant percentage of cash transactions are not anonymous and average person assumes they are.

My assumptions include:

- Knowing how cash is flowing is extremely valuable to governments for a number of reasons; economic, investigations, counterfeits, etc.

- Cash management businesses scan 100% of their cash received or distributed, voluntarily provide that data and meta data to governments, and majority of cash transactions are non recirculated, but withdrawn, used, deposited.

- Governments have a wide-spectrum of resources to trace cash on a bill by bill basis; likely key methods include face scans, serial numbers, and location data via apps/cell.

- Assumption that if you combined all the prior assumptions and fact that many governments have millions to research topic, often leverage their authority, etc — and it is not a stretch to believe governments are able to identify significant percentage cash transactions if prior assumptions are true.

You can track where a bill was distributed, what bank it came from, who withdrew that cash, but past that you can't track any of the transactions that happen. The transactions being tracked is the important part here.

As mentioned in comment you replied too, both cash withdrawals & deposits are scanned — and most cash is only used once between receipt and being spent before entering banks again. For small volume of cash, might be possible to remain anonymous, but for large volumes, it would be extremely hard without there being a cost to doing so and might even be technically money laundering, which is illegal. Most retail locations will not break bills without transactions and will not take unusually large bills for transactions. When combined with other methods of surveillance, such as asset tracking, location-data, security cameras, etc, it’s virtually impossible to stay anonymous at any significant scale.

Core point is like blockchain, people do not realize how traceable cash is and many falsely assume it’s completely anonymous, which it is not.

If a store makes daily deposits and those serial numbers are scanned, you can narrow down the transaction to a day. Security footage will show the transaction happening. It's a bit of work, but if that happens to you twice there aren't too many people who visited the same two stores those two days. They now know what you look like and can find your other movements across other security cameras. Bingo, you were tracked via your cash.

Unless you're also an expert at disguise and also avoiding security cameras to and from the stores. Every time you buy something.

Volume of work required really depends on where money is spent. Many retailers not only scan all faces, but if another method of identifying the customer is not available will use third-party services or government partnerships to identity the customers and tie them to a cash transactions. Few retailers even scan large bills real-time at the point of sale.

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