How to Tell if a Bill Is Fake With a Marker

Counterfeit detection markers are a quick and accessible tool used by individuals and businesses to identify potentially fake bills. They provide a preliminary method to indicate a bill’s authenticity, helping to safeguard financial transactions.

Understanding How Counterfeit Detection Markers Function

Counterfeit detection markers operate on a chemical principle involving iodine. Genuine U.S. currency paper is made from a blend of 75% cotton and 25% linen, a composition that naturally lacks starch. This paper is manufactured exclusively for the U.S. Bureau of Engraving and Printing.

Most common papers, such as those used in printers or photocopiers, are derived from wood pulp and contain starch. The iodine-based ink within a counterfeit marker is designed to react with this starch. When the marker is applied to paper containing starch, a chemical reaction occurs, causing the mark to turn a dark brown or black color.

Conversely, when the marker is used on genuine U.S. currency, the absence of starch in the cotton-linen paper means no chemical reaction takes place. The mark left by the pen will remain faint, clear, or appear as a light amber or yellow color. This color difference provides a quick visual cue, distinguishing between the starch-free paper of real currency and the starch-containing paper often used by counterfeiters.

Applying the Marker and Interpreting Results

To use a counterfeit detection marker, select a lightly colored, unprinted area on the bill, such as the border or an unprinted section of the portrait. This ensures the ink’s reaction is clearly visible without interference from existing printing. Gently draw a small line or mark on this chosen area.

After applying the mark, observe the color change carefully. If the mark remains faint, clear, or turns a light amber or yellow, the bill is likely genuine. This indicates that the paper did not react with the iodine-based ink, consistent with the composition of authentic U.S. currency.

If the mark darkens to a brown or black color, it suggests the bill is counterfeit. This dark coloration results from the marker’s iodine reacting with starch present in the paper, characteristic of common wood-pulp paper often used in fraudulent bills. This visual change serves as an immediate alert.

Recognizing the Marker’s Limitations

Counterfeit detection markers are not infallible. Their effectiveness relies on detecting starch in paper, meaning they may not identify all types of sophisticated counterfeits.

Some counterfeiters use “bill bleaching,” removing ink from genuine, lower-denomination bills and reprinting them with higher denominations. Since the underlying paper is authentic, it lacks starch, and the marker would indicate it as genuine, leading to a false positive. If counterfeiters use specialized papers without starch, the marker would also fail to detect them. The solution within the pens can also degrade over time, reducing accuracy.

Steps for Suspected Counterfeit Bills

If a bill is suspected to be counterfeit, do not return it to the person who passed it. Instead, try to delay the individual if safe, and observe their physical description, any companions, and vehicle details, including license plate numbers.

Limit handling of the suspected bill to preserve evidence. Place it in a protective covering, such as an envelope. Write your initials and the date on the white border areas of the note.

Promptly report the suspected counterfeit currency to local law enforcement or the U.S. Secret Service. They are responsible for investigating counterfeit currency. Surrender the bill only to a properly identified police officer or a U.S. Secret Service agent.