All modern United States currency contains either a 10- or 11-digit serial number in order to make each bill unique. Ten-digit serial numbers were on all bills until the “new style” came out in 1996. Those bills (and all produced since then) have an 11-digit serial. The serial number consists of the following:
- The first letter, only found on the new-style bills, represents the series of the bill. The series indicates the year in which the design of the bill was approved for production. This begins with A, and moves through the alphabet each time a new series is needed (for example, each time there is a new secretary of the treasury, the bill design changes because the secretary’s signature is on all currency). You can also find the series of the bill printed directly to the bottom-right of the portrait.
- The second letter (or first, if you’re looking at an old-style bill) represents the district of the Federal Reserve Bank that your bill was issued from. As there are 12 Federal Reserve Banks, this letter can range from A to L, with A representing Boston, MA, and L representing San Francisco, CA.
- The eight numerical digits that follow represent a unique ID number. This number increases sequentially as each bill is printed. Using these digits alone, there would be a possible 99,999,999 bills issued per bank.
- The final letter is used to raise the number of possible bills beyond 99,999,999. Altogether, there are a possible 2,499,999,975 serial numbers for each bank!
As quality control finds defective notes in the printing process after the serial number has been overprinted, they are taken out with their serial number written down and replaced with another banknote printed specifically for this purpose, so that the number of banknotes being printed stays the same in each production batch. With replacements notes, a set of serial numbers can still have the proper number of bills even if some of the original bills had to be pulled. The replacement notes have a sequence of their own, using the star as their final “letter.” This allows for 99,999,999 possible replacement notes for any given bank, series and denomination. This saves time and money compared to re-printing exactly the same serial number that was used before. It is rare that the replacement banknote has the same serial number as the original faulty one. A replacement note will have its own serial numbering system that separates it from the normal numbering system.
A star note is also a bank note that has an asterisk (*), or star, after the serial number. Many early issues carried the star in front of the serial number. These have been used by various countries around the world including Australia and the United States. In the US, the Bureau of Engraving and Printing inspects currency for printing errors prior to releasing notes into general circulation. When notes are discovered that have been printed incorrectly (such as having the serial numbers upside down, etc.) the misprinted “error notes” are replaced with star notes because no two bills within a certain series can be produced with the same serial number. They are used to maintain a correct count of notes in a serial number run. By their nature, star notes are more scarce than notes with standard serial numbers and as such are widely collected by numismatists.
A star note was also substituted for the last note in a block rather than printing a note with a serial number consisting of eight zeros. This practice is no longer in use, as the highest range of serial numbers is now reserved for uncut sheets sold to collectors, so regular notes intended for circulation do not reach the final serial number in the block.
In general, replacement notes aren’t worth more than regular bills. However, if you find a replacement note with a particularly interesting serial number — like 00000001 or 999999999 — or a large number of consecutively numbered replacement notes that you keep together as a lot, you may have a collector’s item on your hands.