ABA Routing Number

An ABA Routing Number is a nine digit number (eight digits plus a check digit) which identifies a specific financial institution in the US.

They are sometimes referred to as bank “Transit Numbers” in other countries, such as Canada. However, there is also a portion of an ABA Routing Number that is referred to as the “Transit Number”.

US Bank Routing Numbers are not specific to US Banks, but may be assigned to foreign banks located within the US or thier annexes.

Routing numbers are administered by the Routing Number Administrative Board under the sponsorship of the American Bankers Association.

The ABA transit number appears in two forms on a standard check – the fraction form and the MICR (magnetic ink character recognition) form.

Both forms give essentially the same information, though there are slight differences.

The MICR forms are the main form – it is printed in magnetic ink, and is machine-readable; it appears at the bottom left of a check, and consists of nine digits.

The fraction form was used for manual processing before the invention of the MICR line, and still serves as a backup in check processing should the MICR line become illegible or torn; it generally appears in the upper right part of a check near the date.

The MICR number is of the form

where XXXX is Federal Reserve Routing Symbol, YYYY is ABA Institution Identifier, and C is the Check Digit, while the fraction is of the form:

where PP is a 1 or 2 digit Prefix, no longer used in processing, but still printed. Sometimes a branch number or the account number are printed below the fraction form; branch number is not used in processing, while the account number is listed in MICR form at the bottom. Further, the Federal Reserve Routing Symbol and ABA Institution Identifier may have fewer than 4 digits in the fraction form. The essential data, shared by both forms, is the Federal Reserve Routing Symbol (XXXX), and the ABA Institution Identifier (YYYY), and these are usually the same in both the fraction form and the MICR, with only the order and format switched (and left-padded with 0s to ensure that they are 4 digits long).

The prefix and the Federal Reserve Routing Symbol (XXXX) are determined by the bank’s geographical location and treatment by the Federal Reserve type, while the remaining data (YYYY, and Branch number, if present) depends on the specific bank, and are unique within a Federal Reserve district.

In the check depicted above right, the fraction form is 11-3167/1210 (with 01 below it) and MICR form is 129131673 which are analyzed as follows:

the prefix 11 corresponds to San Francisco,
3167 (common to both) is the ABA Institution Identifier,
1210 and 1291 are the Federal Reserve Routing Symbols (generally equal, here different probably due to obfuscation, see image file history for more information), with the initial “12″ corresponding to the Federal Reserve Bank of San Francisco, the third digits (“1″ and “9″) corresponding to check processing centers, and the fourth digits (“0″ and “1″) corresponding to where the bank is located – “0″ indicates “in the Federal Reserve city of San Francisco”, while “1″ indicates “in the state of California”.
the final “3″ in the MICR is the check digit, and
the “01″ below the fraction form is the branch number.
In the case of a MICR line that is illegible or torn, the check can be still be processed without the check digit. Typically, a repair strip or sleeve is attached to the check, then a new MICR line is imprinted. Either 021200025 or 0212-0002 (with a hyphen, but no check digit) may be printed, and both are 9 digits. The former (with check digit) is preferred to ensure better accuracy, but requires computing the check digit, while the latter is easily determined by inspection of the fraction, with minimal clerical handling.

MICR Routing number format
The MICR routing number consists of 9 digits:

where XXXX is Federal Reserve Routing Symbol, YYYY is ABA Institution Identifier, and C is the Check Digit.

Federal Reserve Routing Symbol
The Federal Reserve Routing Symbol were originally assigned in the systematic way outlined below, reflecting a bank’s geographical location and internal handling by the Federal Reserve. However, the link is today tenuous – following banking consolidation, many banks use a routing number from a now-defunct bank, while the Federal Reserve no longer assigns specific numbers for thrifts, nor does the “check processing facility” have any current meaning, as check processing is now centralized within each Federal Reserve district.[4]

First two digits
The first two digits of the nine digit ABA 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, and correspond to the 12 Federal Reserve Banks. For example, 0260-0959-3 is the routing number for Bank of America incoming wires in New York, with the initial “02″ indicating the Federal Reserve Bank of New York.
21 through 32 were assigned only to thrift institutions (e.g. credit unions and savings banks) through 1985, but are no longer assigned (thrifts are assigned normal 01–12 numbers). Currently they are still used by the thrift institutions, or their successors, and correspond to the normal routing number, plus 20. (For example, 2260-7352-3 is the routing number for Grand Adirondack Federal Credit Union in New York, with the initial “22″ corresponding to “02″ (New York Fed) plus “20″ (thrift).)
61 through 72 are special purpose routing numbers designated for use by non-bank payment processors and clearinghouses and are termed Electronic Transaction Identifiers (ETIs), and correspond to the normal routing number, plus 60.
80 is used for traveler’s cheques
The first two digits correspond to the 12 Federal Reserve Banks as follows:

(01–12) Thrift
(+20) Electronic
(+60) 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

Third and fourth digits
The third digit corresponds to the Federal Reserve check processing center originally assigned to the bank,[4] while the fourth digit is “0″ if the bank is located in the Federal Reserve city proper, and otherwise is 1–9, according to which state in the Federal Reserve district it is.

If you are taking checks over the Internet, by Phone, Fax, email, or other means, errors can happen by simple typo’s, or blatant attempts of fraud, and should be checked for accuracy.

You can find a free algorithm checker that allows you to instantly analyze any routing number for accuracy

Don’t get caught with bogus or erroneous ABA Routing Numbers, that can cost you a heap of problems, and money, such as Bank return charges, delay of payment, recovery, and other associated costs.

By having your own ABA Routing Numbers List you can avoid expensive problems. provides a tool for locating a missing or erroneous check digits, or validating a routing number through an online validation form. Also available is an option to download all 21,000+ ACH Routing Numbers and the associated Bank information.

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