tl;dr cash can be tracked every time it goes into a machine or gets picked up by an armored car!

Translation provided below to save energy on repeated translations / avoid misunderstandings from subpar services; please support the journalists at netzpolitik if you are able (donation link), and let us know so we can thank you if you do and so I don’t feel as bad about a full text copy

Cash Tracking: Your Wallet Contains a Surveillance Tool

Cash is considered an anonymous means of payment. However, banknote serial numbers can reveal the routes they travel. The infrastructure for cash tracking is constantly expanding, and German security authorities are already using it in their investigations.

July 9, 2025, 06:17 AM - by Martin Schwarzbeck, Marc Lagies - in Surveillance - 40 Comments

(Image of a close-up of various banknotes.) Caption: Every banknote is unique, making it a potential surveillance tool. – All rights reserved Imago/Wolfilser

It’s waiting in your wallet for its next use. It has been on the move for years, reporting its location whenever it’s scanned—which happens quite often. It can make your interests and needs traceable, revealing personal connections and business relationships.

It’s a banknote, a printed strip of cotton fiber with two letters and a ten-digit string of numbers in the top right corner of its back side—its unique serial number. A typical twenty-euro bill, perhaps. Over the course of its life, it is registered at countless locations. It passes through machines for train tickets, parking stubs, snacks, coffee, cigarettes, photos, and gambling. Time and again, it goes through devices that count, check, and sort money. Machines with modern banknote processing modules can track serial numbers.

Even when a human collects the banknote, it is not safe from automated serial number recognition. The daily earnings of most businesses are collected by cash-in-transit companies. And in their cash centers, they run the money through banknote inspection and sorting machines that can also read serial numbers.

The widespread use of automated serial number recognition provides the technical infrastructure for detailed tracking of a banknote’s journey. And there are growing efforts to store and consolidate the resulting data. This is how cash becomes a surveillance tool.

Law enforcement agencies already use serial number tracking for investigations. The industry wants to use it to optimize cash logistics. And curious individuals even track cash as a hobby. “Because it’s fun!” proclaims a website for passionate Euro banknote trackers.

Yet, there are many payments that people prefer to make anonymously: expenses for health problems or sexual activities, for example, but also donations to political organizations. If the bill a high-ranking official withdraws today shows up tomorrow at a workplace for sex workers, it could make them vulnerable to blackmail. If an uncloseted individual uses a tracked banknote to support a queer NGO, it could, in some places, threaten their very existence.

Cash is Popular—Partly for Privacy Reasons

Over 80 percent of Germans see data protection as a reason to use cash. More than two-thirds believe cash is of great importance to society. According to the latest survey, over half of all transactions in 2023 were still conducted with cash. People in Germany are hoarding 395 billion euros in cash.

Privacy advocates warn of a new form of mass surveillance and the immense infringement on fundamental rights that cash tracking potentially represents. The German central bank, the Bundesbank, points out that privacy is an important advantage of cash for many people. Germans have a right to “informational self-determination.” At the same time, the central bank itself tracks the path of certain banknotes on specific occasions. “It must be assumed that serial number reading will become a permanent and irreversible fixture,” it wrote in an internal 2021 document that netzpolitik.org obtained through a freedom of information request.

Anyone who delves into the world of cash tracking begins to see money differently. The bills start to tell stories. In this article, we explore how the cash industry, law enforcement, and central banks worldwide are working on tracking cash. We look at how German police and public prosecutors use cash tracking. And we get to know a little-known startup that collects serial numbers at a central hub of the cash cycle and sells insights from its database to investigative authorities.

“A Promising Technology”

The necessary technology to trace the path of a banknote already exists and is used in numerous countries. The International Association of Currency Affairs (IACA), a lobby group for central banks and cash industry companies, considers cash tracking—known in industry jargon as “Cycle-Cash Visibility and Collaboration”—to be a promising technology. It is intended to make cash management more efficient.

An award for particularly advanced cash tracking solutions, presented by the IACA at the end of May, shows where the industry sees the future. The winner was the Japanese corporation Glory Ltd. for a series of projects in Europe where banks and cash-in-transit companies capture serial numbers and automatically search for numbers involved in criminal activities.

The company also developed Kibango, a software for analyzing and managing serial numbers. Search lists of serial numbers can be imported into it. Every banknote withdrawn from an ATM can be tracked with it, according to the company’s promotional material. If our example twenty-euro bill is on a search list, such software triggers an alarm as soon as it is scanned anywhere.

These Countries Already Track Cash in Detail

China: ATMs must link the serial number of every banknote they dispense to an account. This makes it clear who put each bill into circulation. Some devices even capture biometric data of the person making the withdrawal.

South Africa: The central bank operates a real-time tracking system for cash movements, according to Pearl Kgalegi, head of currency management there, speaking at an IACA conference. Information from ATMs is collected in a central database and shared with security authorities. Since this began, there have been more arrests, for example, after ATM bombings.

Canada: The Canadian central bank maintains a database with data on all Canadian banknotes in circulation to monitor wear and tear. The Bank of Israel also has a banknote database.

USA: A consortium of 10,800 US law enforcement agencies, called the Regional Information Sharing Systems (RISS), operates a network of money-counting machines and a database that stores photos and serial numbers of captured banknotes. Investigators from participating agencies can search this database. According to a RISS brochure, it was used in Hawaii to catch a drug wholesaler after tracking money that had been seized from a customer, registered, and then returned.

German security authorities also currently use registered banknotes as an investigative tool. And right now, there are efforts to take their cash tracking to a whole new level.

The Crimes German Police Pursue with Cash Tracking

German police have been using banknote serial numbers to track cash flows since at least the 1970s. For example, a person is kidnapped, and the kidnappers demand a ransom. Before the money is handed over in a suitcase, police officers record the serial numbers of the bills in a police database. In this database, they also note the serial numbers of banknotes stolen from ATM bombings or armored truck robberies. If large amounts of cash are later found, for instance, at a border crossing or during a house search, police or customs check if any wanted bills are among them. This allows them to draw conclusions about the perpetrators, depending on where the money reappears.

The serial numbers in the police database are also linked to individuals. “In the Police Information Network, it is possible to link different categories of information, including personal data,” writes the Bremen Police. In parallel with storage in the national database, an alert is also created in the Schengen Information System, which allows for Europe-wide searches for banknote serial numbers.

This means that police-registered banknotes are circulating out there. And you might have one in your wallet right now.

Investigators seem reluctant to talk about this tool. The Federal Criminal Police Office (BKA) and state police forces cite tactical reasons for not providing details. The Hamburg Police even deflected a corresponding parliamentary inquiry from Left Party representative Deniz Celik at the end of May. However, from the little that the police authorities have disclosed, it is clear that and how banknote serial numbers are used for investigations.

The Thuringia Police write: “In the pursuit of money laundering, knowledge of serial numbers can help trace illegal cash flows and identify the individuals or organizations involved.” The Bavaria Police cite terrorism financing as an example where cash tracking can “clarify cash flows or their origin.” Police forces in other federal states confirm that banknote serial numbers are recorded and searched for in investigations across various crime areas.

Until now, authorities have had to hope that the wanted banknotes eventually turn up during a police or customs check. The chances are relatively small. This is likely why investigators regularly ask the Bundesbank if it has encountered a specific banknote. This is revealed in an internal 2020 study that netzpolitik.org made public. At the time, the Bundesbank was testing whether it could comprehensively process serial numbers, partly to accommodate investigators. It ultimately decided against it. But investigators can now have the bills searched for in a different database. They might even get connected to a kind of real-time monitoring system of the German cash cycle.

“We Are Basically ‘Listening’ to the Cash”

Gerrit Stehle, CEO of Elephant & Castle IP GmbH, wants to take official cash tracking in Germany to a new level. Stehle offers a constant, automated mass-comparison with circulating banknote serial numbers—an interface into the engine room of the cash infrastructure.

His company receives banknote serial numbers, along with the time and place of their capture, from one of the cash-in-transit companies operating in Germany. These armored trucks are central hubs in the cash cycle—most bills pass through them regularly. As an expert consultant, Gerrit Stehle conducts research for security authorities in this database. Stehle also stores the serial numbers of the bills whose stories he traces for authorities in his system. His company is already working with several German public prosecutor’s offices and with security authorities from other countries, he says.

“Our technology makes it possible to trace the history of banknotes at the push of a button,” says Stehle. It could be determined, for example, how often bills have been in circulation, which ones have disappeared, or which have left the country. “We use data analysis to develop a deep understanding of cash movements and to identify payment flows that show potentially suspicious patterns. We are basically ‘listening’ to the cash,” he says. He has been working on the project for seven years, and it now involves 15 people.

North Rhine-Westphalia’s Public Prosecutor’s Office for Cybercrime (ZAC NRW) has tested the system and presented it in an online training session to specialist prosecutors from the fields of organized crime, fraud, and corruption. ZAC NRW also lends out a money-counting machine that reads serial numbers and offers assistance with data collection. ZAC NRW head Markus Hartmann says the database is an “instrument that has been used in a manageable number of cases.”

For serial number capture, Stehle and his partner company rely on a specific money-counting device from the Japanese manufacturer Glory Ltd., which he says is the most reliable. Stehle shares the information obtained in the form of expert reports with investigative authorities. They can then compare the data with the statements of suspects to uncover inconsistencies or confirm claims. “A real-world example: in one case, a person claimed the money was fresh from the bank, but through our analysis, we were able to prove that the cash was much older,” says Stehle.

Authorities to Get Direct Interface

Ideally, Stehle would like to connect even more checkpoints to his cash surveillance network. “Money-counting devices are already widespread, for example, in the back offices of supermarkets, which offers significant potential. If banknote serial numbers were systematically recorded, robberies targeting the elderly, cash-in-transit vehicles, ATMs, or retail stores would become significantly less attractive.”

Stehle does see the danger. The ability to conduct anonymous transactions “is a fundamental pillar of freedom,” he says. But he also sees the dark side: cash can be misused to support illegal activities.

Stehle’s goal is to make his system directly accessible to investigators through paid software licenses, without the intermediary step of an expert consultant. “Via a user-friendly interface, they could then connect to the system 24/7 and conduct the relevant analyses themselves,” says Stehle.

The cash-in-transit company that provides the data receives no payment for it. “The company benefits because costs can be reduced, as there tend to be fewer attacks, and it can offer this new technology to retailers and banks,” says Stehle. He will not reveal which company he is working with.

The collected data is stored, with copies in multiple locations, in a cloud developed in cooperation with Google and Telekom, says Stehle. There, it is also protected from unauthorized access by US security authorities.

How Sensitive Is the Data?

From a data protection perspective, Stehle sees no problems. “This is non-personal data that is not subject to data protection laws. We do not collect any personal data of citizens,” he says. The GDPR only protects personal data—that is, data relating to a directly or indirectly identifiable person. A lot of other data is not covered, such as weather records. But is data on cash flows really as impersonal as, say, wind speed?

Luke Hoß, a member of the German parliament for the Left party, certainly sees cash tracking as a threat to privacy: “Comprehensive tracking of cash serial numbers would allow for deep insights into people’s private lives. Not just a trip to the bakery, but a drive to a clinic for an abortion would be traceable.” The right to privacy must not be further restricted by citing security concerns, he says. “In the event of an authoritarian party like the AfD taking power, there is a danger that the transactions recorded here could lead to persecution, even if they are legal under current law,” he says.

Although Gerrit Stehle speaks of “non-personal data,” he still shows some understanding that the data is not entirely harmless. “It has a certain potential [for misuse]; such information should not be in private hands,” he says. That is why he only offers his services to government agencies. He says there are already interfaces between police case management tools and his system. “Their tools upload our data into their tools,” he says.

A glimpse of the future Stehle envisions is revealed in an international patent he filed in 2018. He calls it the “nucleus of the project.” In it, Stehle describes a machine that accepts cash and, using the serial numbers on the bills, detects whether the money has been reported stolen or was handed over in a ransom extortion. In the event of such a find, it should be able to automatically notify the police or security services. And at gas stations, according to Stehle’s patent application, deposit machines could automatically trigger the storage of corresponding video footage if wanted money is found.

Head of Customs Union Demands Comprehensive Cash Tracking

Frank Buckenhofer, chairman of the police union within the German customs authority (GdP-Zoll), is a passionate advocate for cash tracking technology. “Banks and cash courier services record the numbers of banknotes and their temporal-spatial assignment. It would be helpful if this data were consolidated and made available to police and customs authorities,” he says. The data would create a relatively dense network of important information about the path and origin of cash. “And because the mere numbers are not personal data, data protection is not an issue either,” he claims. The Data Protection Commissioner of Schleswig-Holstein sees it differently—more on that in a moment.

If larger amounts of cash are found by police and customs authorities, Buckenhofer hopes, registered serial numbers could be used to find contradictions in statements. “For example, if someone is caught at the border with a million euros in cash or more, which happens time and again, they can tell the officers any story. For instance, that it’s ‘savings from grandma’,” says Buckenhofer. But if a money-counting machine then identifies bills that were in many different ATMs, at gas stations, or supermarkets in the last 48 hours, the money courier’s story collapses. “So we urgently need this data; otherwise, people can just feed us a pack of lies.”

The technology could also be used to track down former ransom money and cash from cracked ATMs. The search for suspects can be intensified in regions where wanted banknotes appear. “The systematic recording of banknotes in a database enables a whole range of uses for the criminal investigation work of customs and police,” says Buckenhofer. He would like to see laws for cash tracking and a private-sector serial number database that customs, police, tax, financial, and anti-money laundering authorities can access online.

Data Protection Commissioner Concerned

Marit Hansen, the State Commissioner for Data Protection in Schleswig-Holstein, is critical of comprehensive cash tracking. She says: “If serial numbers are stored with the time and place of their capture, and this data is collected with increasing granularity, we lose the anonymity of cash.” Even if each instance of data collection serves a legitimate interest, it can be problematic. “When viewed as a whole, there is a risk that the individual data points could be linked to a person. Above a certain threshold, a person’s location data could be derived, for example. Likewise, it could then be determined who is interested in what,” she says.

Comprehensive cash tracking creates risks not only for individuals but also for trade secrets and possibly even for national security, says Hansen. For example, it could be used to obtain intelligence-relevant information about security-sensitive individuals.

Hansen compares the serial numbers to the printer identification codes, so-called Yellow Dots, that are embedded in color printouts. “Those are also just technical data at first, yet they can be used, for example, to identify whistleblowers.”

Hansen believes it is important that people have a truly anonymous payment option available to them. Payment trails can reveal personal or even intimate details: more or less healthy diets, addictions, love affairs. “This is information that is nobody else’s business. People have a legitimate interest in not leaving a trace here,” she says.

In a future installment of this investigation, we will trace the life of a banknote from printing to shredding and see all the places where serial numbers are already being recorded. This journey through the cash cycle impressively demonstrates how the impending network of data points would de-anonymize cash.