# Why Do Some U.S. Bills Have a Star at the End of the Serial Number?

By: HowStuffWorks.com Contributors  |

­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 and L representing San Francisco.
• 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.

On occasion, a bill shows up that has a small star in place of the final letter in the serial, and many early issues carried the star in front of the serial number.