A supernote is a counterfeit version of American currency which is so skillfully produced that it is difficult to distinguish from the real thing. Supernotes are extremely frustrating for businesses which handle American currency, especially since these bills cannot be detected using most basic anti-counterfeiting methods, such as specialized pens or the old retail trick of rubbing a nail along the portrait to check for the distinctive raised print of a real American banknote. In response to the supernote problem, the American treasury has overhauled currency designs several times, but new versions of these counterfeits continue to emerge.
Most counterfeit currency is detectable, although sometimes it takes a little bit of work. This is because two of the key aspects of the process used to produce banknotes by the United States Government are difficult to replicate. The first is the highly specialized paper, which is produced only for the Mint using a secret process which embeds colored and holographic threads in the paper. The second is the intaligo printing process, the same process which creates the ridges in the engravings which people associate with authentic banknotes.
A number of other anti-counterfeiting measures are also used in American currency, but the difficulty involved in copying the paper and the printing technique is generally enough to deter most counterfeiters. In the case of supernotes, however, skilled engineers have replicated the expensive intaligo process, and they have been able to produce a credible facsimile of the paper used for official banknotes. They have also copied many of the unique details of American currency, ensuring that in addition to passing casual inspection, a supernote can also evade detection at some financial institutions.
Most supernotes appear to be $100 US bills, which is also a bit unusual for counterfeiting operations, many of which stick with $20 US bills, since these are easier to distribute. The bulk of these bills also appear to be in circulation overseas, with the first supernote being detected outside the United States in 1990, although more supernotes are showing up within American borders each year.
The source of supernotes is a mystery, despite extensive investigation. The level of skill involved has led some people to suggest that they are the work of a foreign government such as North Korea or Iran, perhaps with the goal of destabilizing the American economy. However, no one has positively traced supernotes back to these sources, and no credible evidence to connect these bills with any other individuals or groups has been uncovered.
On the consumer level, there isn't much to be done about supernotes. If a bill feels slightly strange or looks off, it may be a supernote, in which case it should be taken to a bank for examination, but most consumers don't catch supernotes when they receive them, and they may unwittingly pass them on into circulation. Businesses likewise have little defense against the supernote, and since $100 US bills are legal tender, a business cannot refuse to accept them to avoid counterfeit bills.
