Counterfeit money can be detected through a combination of touch, visual inspection, and simple tools like UV lights or magnifying glasses. The good news: counterfeiting is rare. Federal Reserve data estimates that only about 1 in 80,000 notes in U.S. domestic circulation is counterfeit, and for the denominations most commonly handled by consumers, the rate of fakes that can pass basic examination is well below 1 in 100,000. Still, knowing what to look for means you can spot a bad bill in seconds.
The Feel Test Catches Most Fakes
Genuine U.S. currency is printed on a blend of cotton and linen, not wood-pulp paper. This gives it a distinctive texture that’s slightly rough, crisp, and resistant to tearing. Most counterfeits are printed on standard paper or card stock, which feels smoother and flimsier. If a bill feels off in your hand, that instinct is worth trusting. Around the world, bank tellers in countries that handle large volumes of U.S. dollars still rely primarily on touch and sight as their first line of defense.
Run your fingernail across the jacket of the portrait on a $5 bill or higher. Genuine bills are printed using a technique called intaglio, which leaves raised ink you can physically feel. Counterfeit bills printed on standard inkjet or laser printers produce a flat surface. This single check catches a large percentage of low-quality fakes.
Visual Features to Check by Hand
Every U.S. bill $5 and above includes a set of visual security features designed to be easy for the public to verify without any equipment.
- Color-shifting ink: On $10, $20, $50, and $100 bills, the numeral in the lower-right corner changes color when you tilt the bill. It typically shifts between copper and green (or gold and green on the $100). Photocopiers and printers can’t replicate this effect.
- Watermark: Hold the bill up to a light source. You should see a faint image that matches the portrait on the front. It’s embedded in the paper itself, not printed on the surface, so it’s visible from both sides.
- Security thread: Also visible when held to light, a thin embedded strip runs vertically through the bill. Its position varies by denomination. On a $20, it’s to the left of the portrait; on a $100, it’s to the right. The strip glows a specific color under ultraviolet light (blue for the $5, orange for the $10, green for the $20, yellow for the $50, pink for the $100).
- Microprinting: With a magnifying glass, you can find tiny printed words in several locations on bills $5 and higher. These words correspond to the denomination or contain phrases like “THE UNITED STATES OF AMERICA,” “USA,” or “E PLURIBUS UNUM.” Standard printers can’t reproduce text this small clearly, so on a counterfeit, microprinting typically appears blurred or as a solid line.
Euro banknotes in the Europa series carry a similar layered approach. They include a portrait watermark, a portrait window (a transparent section in the hologram that shows the mythological figure Europa when held to light), a hologram strip with a satellite pattern that moves when tilted, and an “emerald number” that shifts from emerald green to deep blue as you change the viewing angle.
Counterfeit Detection Pens and Their Limits
The cheap marker-style pens sold at office supply stores use an iodine solution that reacts with starch. When you swipe the pen on regular wood-pulp paper, the starch in the paper triggers a dark brown or black mark. On genuine currency’s cotton-linen blend, the mark stays light or amber, indicating no starch is present.
These pens are popular because they’re fast and cost a few dollars. But they have a significant blind spot. A counterfeiter who prints on any starch-free paper, even a bleached lower-denomination bill reprinted as a higher one, will pass the pen test. The pen checks the paper chemistry, not whether the bill’s design is authentic. It’s a useful first filter, not a definitive test.
How Machines Detect Fakes
Businesses that handle large volumes of cash use automated bill validators and counters that go far beyond what the human eye can see. These machines typically combine several detection methods at once: ultraviolet light analysis, magnetic ink sensing, and infrared imaging.
Infrared detection is particularly powerful. Genuine banknotes, including both U.S. dollars and euros, are printed with two types of ink: one that reflects infrared light and one that absorbs it. Under an infrared camera, a real bill displays a distinctive pattern of dark and light zones that varies by denomination. A photocopy or inkjet print might look identical to a genuine bill in visible light, but under infrared, the forgery is immediately obvious because standard printer inks don’t replicate this dual-ink behavior. Research published in the journal Sensors confirmed that near-infrared imaging can effectively catch real-world forgeries that are undetectable under normal light.
UV lights, which are built into many countertop detectors, cause the embedded security thread to fluoresce in a denomination-specific color. They also reveal that genuine currency paper doesn’t glow brightly under UV the way standard white paper does (most commercial paper contains optical brighteners that fluoresce blue-white). If the whole bill lights up under a blacklight, it’s likely fake.
The “Supernote” Problem
Not all counterfeits are crude. The most famous example is a family of counterfeit $100 bills known as the “Supernote” or “Superdollar,” which the Secret Service has called the most technically sophisticated counterfeit in its history. These notes were reportedly produced using professional-grade printing equipment and high-quality paper, making them difficult to detect with basic tools like pens or magnifying glasses. Investigating and suppressing the Supernote required an unprecedented forensic effort involving the Secret Service, other government agencies, and national laboratories.
For everyday situations, though, Supernote-quality counterfeits are extraordinarily rare. The vast majority of fakes in circulation are produced on commercial printers and can be caught with the visual and tactile checks described above. The $102 million in counterfeit currency that passed to the public worldwide in fiscal year 2023 sounds like a lot, but it represents a tiny fraction of the roughly $2.3 trillion in genuine U.S. banknotes in circulation.
Quick Routine for Checking a Bill
You don’t need to run through every security feature every time you receive change. A fast three-step check covers the most ground:
- Feel it: Does the paper feel like cotton-linen blend, with raised ink on the portrait?
- Tilt it: Does the color-shifting numeral change color? Does the holographic strip (on the $100) shift as you move it?
- Hold it to light: Can you see the watermark and the security thread in the correct positions?
If a bill fails any of these, compare it side by side with another bill of the same denomination. Differences in color, sharpness, or paper texture become much more obvious in direct comparison.
What to Do With a Suspect Bill
If you believe you’ve received a counterfeit, don’t try to spend it or return it to whoever gave it to you. Handle it as little as possible to preserve any fingerprint evidence. If you’re associated with a financial institution or business, you can report the bill using Secret Service Form 1604. Individuals should contact their local U.S. Secret Service field office directly. As of November 2024, the Secret Service no longer accepts electronic submissions of suspected counterfeits through its website, so phone or in-person reporting is the current process.