In the United States, an ABA routing transit number (ABA RTN) is a nine-digit code printed on the bottom of checks to identify the financial institution on which it was drawn. The American Bankers Association (ABA) developed the system in 1910 to facilitate the sorting, bundling, and delivering of paper checks to the drawer's (check writer's) bank for debit to the drawer's account.
Newer electronic payment methods continue to rely on ABA RTNs to identify the paying bank or other financial institution. Federal Reserve payment services use routing numbers to identify participants in Fedwire Funds Service, Fedwire Securities Service, and FedACH transactions.
Management Since 1911, the American Bankers Association has partnered with a series of registrars, currently Accuity, to manage the ABA routing number system. Accuity is the Official Routing Number Registrar and is responsible for assigning ABA RTNs and managing the ABA RTN system. Accuity publishes the American Bankers Association Key to Routing Numbers semi-annually. The "Key Book" contains the listing of all ABA RTNs that have been assigned.
There are approximately 26,895 active ABA RTNs currently in use. Every financial institution in the United States has at least one. The Routing Number PolicyRouting Number Policy allows for up to five ABA RTNs to be assigned to a financial institution. Many institutions have more than five ABA RTNs as a result of mergers.
ABA RTNs are only for use in payment transactions within the United States. They are used on paper check, wire transfers, and ACH transactions. On a paper check, the ABA RTN is usually the middle set of nine numbers printed at the bottom of the check. Domestic transfers that use the ABA RTN will usually be returned to the paying bank. The same bank may use different routing numbers for checks vs. wire transfers.
Incoming international wire transfers also use a BIC code, also known as a SWIFT code, as they are administered by the Society for Worldwide Interbank Financial Telecommunication (SWIFT) and defined by ISO 9362. In addition, many international financial institutions use an IBAN code.
The IBAN was originally developed to facilitate payments within the European Union but the format is flexible enough to be applied globally. It consists of an ISO 3166-1 alpha-2 country code, followed by two check digits that are calculated using a mod-97 technique, and Basic Bank Account Number (BBAN) with up to thirty alphanumeric characters. The BBAN includes the domestic bank account number and potentially routing information. The national banking communities decide individually on a fixed length for all BBAN in their country.
History The bank numbers in the United States were originated by the American Bankers Association (ABA) in 1911. Banks had been disagreeing on identification. The ABA arranged a meeting of clearing house managers in Chicago in December 1910. The gathering chose a committee to assign each bank in the country convenient numbers to use. In May 1911, the American Bankers Association released the codes.McNally, p. V The numerical committee was W. G. Schroeder, C. R. McKay, and J. A. Walker.McNally, p. VIII The publisher of the new directory was Rand-McNally and Company.McNally, p. III The ABA clearing house codes are like the sub-headings in a decimal outline. The prefixes mean locations and the suffixes banking firms within those locations. Half of the prefixes represent major cities the other half represent regions of the United States. Lower prefixes are used for higher populations, first based on the 1910 U. S. Census. Likewise, within each prefix area banks are numbered in order of city population and bank seniority, although single-bank towns are numbered in alphabetical order. When a new bank is being organized, the current publisher of the directory of banks assigns it a transit code.McNally, pp. V-VI The American Bankers Association asked banks to use the directory exclusively so banks would agree on how to sort checks.McNally, pp. VI-VIII The book was abbreviated Key to Numerical System of The American Bankers Association, and as the Key. It was published by Rand McNally & Co.McNally, p. VI In 1952 Rand McNally moved its corporate headquarters to Skokie, Illinois, and became more interested in publishing maps.RM Acq, p. Our History Also in Skokie is a company called Accuity, which from its history has been the official registrar of ABA bank numbers since 1911. By 2014 it was the publisher of the semi-annual ABA Key to Routing Numbers and was owned by Reed Business Information, British publisher of reference works for professionals, which in turn is owned by Reed-Elsevier, English-Dutch publisher of online format reference works for professionals.Acuity, Bankers', p. About usReed Elsevier, p. Our history Over the years the ABA's identification numbers for banks accommodated the Federal Reserve Act, the Expedited Funds Act and the Check 21 Act. By 2014 the Key included the U. S. Federal Reserve's nine-digit magnetic-ink routing numbers.ABA, p. Key to Routing Numbers—Accuity
Formats
The ABA RTN 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 XXXXYYYYC 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: PP-YYYY/XXXX where PP is a 1 or 2 digit Prefix, no longer used in processing, but still printed, representing the bank's check processing center location, with 1 through 49 for processing centers located in a major city, and 50 through 99 representing processing is done at a non-major city in a particular state. 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 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 nine digits: XXXXYYYYC where XXXX is Federal Reserve Routing Symbol, YYYY is ABA Institution Identifier, and C is the check digit.
Federal Reserve The Federal Reserve uses the ABA RTN system for processing its customers' payments. The ABA RTNs were originally assigned in the systematic way outlined below, reflecting a financial institution's geographical location and internal handling by the Federal Reserve. Following consolidation of the Federal Reserve's check processing facilities, and the consolidation in the banking industry, the RTN a financial institution uses may not reflect the "Fed District" where the financial institution's place of business is located. Check processing is now centralized at the Federal Reserve Bank of Atlanta.
The first two digits of the nine digit RTN 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 checks
The first two digits correspond to the 12 Federal Reserve Banks as follows:
Primary(01–12) Thrift(+20) Electronic(+60) Federal Reserve Bank01 21 61 Boston02 22 62 New York03 23 63 Philadelphia04 24 64 Cleveland05 25 65 Richmond06 26 66 Atlanta07 27 67 Chicago08 28 68 St. Louis09 29 69 Minneapolis10 30 70 Kansas City11 31 71 Dallas12 32 72 San Francisco
The third digit corresponds to the Federal Reserve check processing center originally assigned to the bank.
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.
ABA Institution Identifier The fifth through eighth digits constitute the bank's unique ABA identity within the given Federal Reserve district.
Check digit The ninth, check digit provides a checksum test using a position-weighted sum of each of the digits. High-speed check-sorting equipment will typically verify the checksum and if it fails, route the item to a reject pocket for manual examination, repair, and re-sorting. Mis-routings to an incorrect bank are thus greatly reduced.
The following condition must hold:
(Mod or modulo is the remainder of a division operation.)