ABA routing transit number
A routing transit number (RTN) or ABA number is the nine digit code on the bottom of negotiable instruments such as checks that identifies which financial institution it is drawn upon. This code is also used by the Automated Clearing House to process direct deposits and other automated transfers. This system is named after the American Bankers Association, which designed it in 1910.
Managment of ABAs
Accuity, a SourceMedia company, formerly Thompson Financial Publishing is responsible for assigning new ABAs. They have published this list in the American Bankers Association Key to Routing Numbers semi-annually since 1911.
- There are approximately 30,000 ABA numbers currently in use.
- Lyons Commercial Data maintains an up-to-date bank routing number database and provides access through a web interface, databases, and web services.
Internal checkusms
The first two digits of this nine digit number must be in the ranges 00 through 12, 21 through 32, 61 through 72, or 80.
The digits are assigned as follows
- 00 is used by the United States Government
- 01 through 12 are the "normal" routing numbers
- 21 through 32 were assigned only to thrift institutions through 1985, but now may be used by any bank (but are primarily used by credit unions)
- 61 through 72 are used for electronic transactions
- 80 is used for traveler's cheques
Current routing digits in use
In each of these three ranges, the 12 digit pairs correspond to the 12 Federal Reserve Banks as follows
| Primary | Thrift | Electronic | Federal Reserve Bank |
|---|---|---|---|
| 01 | 21 | 61 | Boston |
| 02 | 22 | 62 | New York |
| 03 | 23 | 63 | Philadelphia |
| 04 | 24 | 64 | Cleveland |
| 05 | 25 | 65 | Richmond |
| 06 | 26 | 66 | Atlanta |
| 07 | 27 | 67 | Chicago |
| 08 | 28 | 68 | St. Louis |
| 09 | 29 | 69 | Minneapolis |
| 10 | 30 | 70 | Kansas City |
| 11 | 31 | 71 | Dallas |
| 12 | 32 | 72 | San Francisco |
Additionally, this number must pass a checksum test using a position-weighted sum of the digits.
- The following condition must hold: .
See also