Can Fake Money Pass the Marker Test?

Counterfeit money presents a persistent challenge in financial transactions, making it important to verify the authenticity of currency received. A common initial defense against fake bills involves the use of counterfeit detection pens. These tools offer a quick method for individuals and businesses to assess whether a banknote is genuine.

How Counterfeit Detection Pens Work

Counterfeit detection pens contain an iodine-based solution that reacts chemically with certain types of paper. Genuine U.S. currency is printed on a unique blend of cotton and linen fibers, which does not contain starch.

Most common paper, like that used for printing, is wood-based and contains starch. When applied to starch-containing paper, the iodine solution causes a chemical reaction resulting in a dark mark (black, brown, or dark blue). If the bill is genuine, the mark from the pen will remain faint, clear, or turn a pale yellow, indicating the absence of starch.

Why Counterfeit Bills Can Pass the Pen Test

Counterfeit detection pens are not foolproof; sophisticated counterfeiters have developed methods to bypass them. One technique involves “bleached bills,” where lower-denomination genuine currency is stripped of ink, and higher denominations are printed onto this authentic paper. Since the underlying paper is legitimate, it lacks starch, causing the pen to register it as genuine despite the fraudulent denomination.

Another method uses paper that naturally lacks starch or treats standard paper to prevent the iodine reaction. Counterfeiters might source specialized starch-free paper or apply chemical coatings (e.g., PVA, gelatin, hairspray) to create a barrier on the surface. These coatings prevent the pen’s iodine solution from reacting with any starch present, allowing a fake bill to pass the pen test.

The pen test primarily targets unsophisticated counterfeits produced on common wood-based printer paper. Professional counterfeiters are aware of this vulnerability and employ advanced techniques to circulate fraudulent currency. This limits the pen’s reliability, as it cannot detect counterfeits produced on authentic or specially treated paper, necessitating more comprehensive inspection methods.

Beyond the Pen: Other Ways to Identify Counterfeit Currency

Since counterfeit detection pens have limitations, a comprehensive approach to identifying genuine currency involves examining multiple security features embedded within the bills.

Tactile Feel: Authentic U.S. currency, made from a cotton-linen blend, has a distinct, slightly rough texture. Counterfeit bills often feel smoother.
Watermark: Hold the bill to light. A faint image, matching the portrait, should be visible in the blank space on denominations $5 and higher.
Security Thread: A thin embedded strip becomes visible when held to light, running vertically. It contains microprinted text and glows a specific color under UV light (e.g., $5 blue, $20 green).
Color-Shifting Ink: On denominations $10 and higher, the numeral in the lower right corner changes color from copper to green when tilted.
Microprinting: Tiny words or numbers, difficult to replicate, are found in various locations and often require magnification.
Red and Blue Fibers: Genuine bills contain small, randomly dispersed red and blue fibers embedded within the paper.
Serial Number: Check the unique serial number on each bill to ensure it matches Federal Reserve indicators.

Relying on a combination of these features offers a more robust defense against counterfeit currency than any single test.

What to Do with Suspected Counterfeit Money

If you suspect counterfeit money, handle the situation carefully to protect yourself and aid law enforcement. Do not return the suspected counterfeit bill to the passer, as this could be dangerous or implicate you in a crime. Instead, observe and remember details about the individual (e.g., physical description, vehicle information) without drawing attention or risking your safety.

Limit direct handling of the bill to preserve any potential fingerprints or other evidence. Place the suspect note into an envelope or other protective covering. Promptly contact your local police department or the nearest U.S. Secret Service field office to report the incident. Only surrender the suspected counterfeit currency to a uniformed police officer or a Secret Service agent, ensuring you note the date and how you received the bill.