United States currency is the most counterfeited currency in the world with Canadian money a close second, these currencies popular due to their status as a ‘hard’ currency, similar to gold. Large numbers of bills in all denominations are counterfeited and passed (given as payment) to unsuspecting merchants and banking institutions. In the past, only large denominations like the $100 and $50 bill were counterfeited. Currently, however, numerous businesses report the receipt of counterfeit $5, $10, and $20 notes with the $20 note being passed with the highest frequency. One of the most common types of counterfeit detection is provided by ultraviolet (uv) light. The operating principle is simple; if the bill being checked has fluorescence then it is genuine. The idea behind this is that the paper used in the printing of real currency has a high starch content making it appear dull under uv light. Counterfeiters generally use bond paper that has virtually no starch and is bleached. The bleached bond paper fluoresces under uv light.