How to Use a Pen to Check if Money is Real

Counterfeit currency poses a challenge in financial transactions, making it important to verify the authenticity of currency. Counterfeit detection pens offer a widely accessible and straightforward initial tool for this purpose. Understanding how these pens operate and their limitations can help in identifying fake bills, although they are part of a broader approach to currency verification.

How Counterfeit Detection Pens Function

Counterfeit detection pens contain an iodine-based ink solution designed to react with specific paper compositions. Genuine United States currency is printed on a unique blend of 75% cotton and 25% linen fibers, which is starch-free. In contrast, most common papers, like those often used by counterfeiters, are wood-based and contain starch.

When the iodine solution from the pen comes into contact with starch, a chemical reaction occurs, causing the mark to turn a dark color, typically brown or black. If the paper is genuine and lacks starch, the mark will remain clear or appear as a light yellow or amber shade. This chemical distinction allows the pen to differentiate between authentic currency paper and ordinary paper.

Applying the Pen and Understanding Outcomes

Using a counterfeit detection pen involves a simple process to check a bill’s authenticity. Draw a small, light line on an unprinted area of the bill, such as the border or the portrait’s white space. A firm but gentle stroke is sufficient. The reaction typically appears almost immediately.

If the mark remains clear or changes to a pale yellow or light amber color, the bill is likely genuine. This outcome indicates the absence of starch in the paper. Conversely, if the mark turns dark brown or black, it suggests the presence of starch, indicating the bill is likely counterfeit.

Constraints of Pen-Based Detection

While counterfeit detection pens offer a quick initial check, they are not foolproof. The pen solely detects the presence of starch, which means it only verifies the paper’s composition, not other sophisticated security features.

For instance, a common counterfeiting method involves “bleaching” lower-denomination genuine bills, such as a $5 bill, to remove the ink and then reprinting them as higher denominations. Since the underlying paper is authentic, these “bleached” bills will pass the pen test, as they are printed on starch-free currency paper.

Additionally, some sophisticated counterfeiters might treat their paper to neutralize starch or obtain paper with a similar cotton-linen blend. Such methods can bypass the pen’s detection, leading to false negatives. Environmental factors like humidity or temperature, and the pen’s age, can also affect its accuracy.

Other Ways to Verify Currency Authenticity

Given the limitations of detection pens, examine other security features embedded in genuine U.S. currency. These features are designed to be difficult to replicate and provide more robust indicators of authenticity.

Raised printing: Feel the slightly rough texture of portraits, borders, and lettering, a result of the intaglio printing process.
Watermark: Hold the bill to light to reveal a faint image, typically matching the portrait on denominations $10 and higher, or the numeral on the $5 bill.
Security thread: A vertical thread embedded in the paper becomes visible when held to light. It is inscribed with text and numbers specific to the denomination and glows a distinct color under ultraviolet (UV) light.
Color-shifting ink: On denominations $10 and higher, tilting the bill reveals the numeral in the lower right corner changing color (e.g., from copper to green). On the $100 bill, the Bell in the Inkwell also exhibits this effect.
Microprinting: Tiny text appears in various locations, such as borders or within the portrait, requiring magnification to be seen clearly. These minuscule words, like “THE UNITED STATES OF AMERICA” or the denomination, are illegible on most counterfeits.

Actions for Suspected Counterfeit Bills

If you suspect you have received a counterfeit bill, follow these steps to prevent its recirculation and assist authorities.

Do not return the bill to the person who gave it to you.
Observe the individual who passed the bill. Note distinguishing characteristics, such as their appearance, companions, or vehicle.
Handle the suspected counterfeit bill as little as possible to preserve any potential evidence.
Place it in an envelope or a plastic bag.
Promptly contact your local police department or the nearest U.S. Secret Service field office.
Financial institutions and businesses typically have procedures for reporting suspected counterfeit currency, often involving Secret Service Form 1604.
Individuals are generally advised to submit suspected counterfeit currency to their local police, who will then forward it to the Secret Service for investigation.