A geocache note is a note of currency that is placed in and/or found in a geocache.
Within the United States, a one-dollar note is usually the most common type of geocache note as it is the least valuable note printed for legal tender and most-readily available. Often a one-dollar note is placed in a geocache when a finder wishes to take an item from the cache but has no comparable item to trade. The one-dollar note is usually then taken from the finder's cash stash (i.e. wallet) and placed in the geocache in order to feel that an equitable trade has been made.
Other currency found in geocaches tend to be more deliberately placed. Two-dollar U.S. notes are somewhat common as it is a rarer note, but not difficult to obtain. Foreign currency is also a popular item, although probably not as common due to the fact that the lowest-valued note of many nations are usually higher in value than one-dollar and even two-dollar notes. Instead, foreign coins tend to be more common.
Often a geocache note is part of the original contents of a geocache with the intent of being a first-to-find prize. Microcaches usually are limited to a one-dollar note as such a prize. Regular-size geocaches may use a more valuable note as the first-to-find prize.
Since paper currency is indeed paper, geocache notes tend to be vulnerable to weather elements. If a note is deliberately planned for a geocache placement, some level of protection is advisable. One good method is to place the note inside a snack-sized self-sealing bag. More elaborate methods are available, but tend to be avoided due to additional costs.
Another common reason behind the placement of geocache notes is due to the Where's George? website, which allows for tracking of U.S. currency via the serial number of such notes. In this way, a geocache note can be regarded as a hitchhiker as its path can be plotted. While this is not the original intent of the Where's George? website, it is still used in this manner.