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A routing transit number (RTN) is a nine digit bank code, used in the United States, which appears on the bottom of negotiable instruments such as checks identifying the financial institution on which it was drawn. This code was designed to facilitate the sorting, bundling, and shipment of paper checks back to the drawer's (check writer's) account.
Since 1911, the American Bankers Association has assigned transit numbers through a series of registrars, currently Accuity. The company is responsible for assigning new ABA numbers. Accuity publishes the ABA Number Directory in the American Bankers Association Key to Routing Numbers semi-annually.
There are approximately 26,895 active routing and transit numbers currently in use. Every financial institution in the United States has at least one of these. Multiple RTNs may result from mergers.
ABA numbers are only for use in domestic transactions within the United States and are of two types, one for funds being debited or credited to or from accounts and one that is used for wire transfers. They are different and usually the ABA number on a check book which is usually the middle set of nine numbers printed at the bottom of the check is the former. Domestic transfers that use the debit/credit routing number will usually be returned to the sending bank. Incoming international wire transfers use a different code system administered by the Society for Worldwide Interbank Financial Telecommunication (SWIFT). The code is called SWIFT-BIC, BIC code, SWIFT ID or SWIFT code more of which can be read about under ISO 9362. There are a number of overlapping issues between these codes and complicating the matter is the fact that European Banks 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.
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:
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 handlings.
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.
The Federal Reserve Routing Numbers 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.
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:
The first two digits correspond to the 12 Federal Reserve Banks as follows:
|Federal Reserve Bank|
The third digit corresponds to the Federal Reserve check processing center originally assigned to the bank, 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.
The 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:
In terms of weights, this is 371 371 371. This allows one to catch any single-digit error (incorrectly inputting one digit), together with most transposition errors. 1, 3, and 7 are used because they (together with 9) are coprime to 10; using a coefficient that is divisible by 2 or 5 would lose information (because ), and thus would not catch some substitution errors. These do not catch transpositions of two digits that differ by 5 (0 and 5, 1 and 6, 2 and 7, 3 and 8, 4 and 9), but captures other transposition errors.
The following formula can be used to generate the ninth digit in the checksum:
This is just moving all terms other than to the right hand side of the equation, which inverts the coefficients with respect to 10 ().
Following the above example for the Bank of America routing number 111000025,
This checksum is very easy to represent in computer programming languages. The following Python example will print "True" when the checksum is valid:
d = "111000025" d = [int(c) for c in d] checksum = ( # do the math! 7 * (d + d + d) + 3 * (d + d + d) + 9 * (d + d) ) % 10 print(d == checksum)
If your computer cannot display this character, it may be seen here.
The numerator consists of two parts separated by a dash. The prefix (no longer used in check processing, yet still printed on most checks) is a 1 or 2 digit code (P or PP) indicating the region where the bank is located. The numbers 1 to 49 are cities, assigned by size of the cities in 1910. The numbers 50 to 99 are states, assigned in a rough spatial geographic order, and are used for banks located outside one of the 49 numbered cities.
The second part of the numerator (after the dash) is the bank's ABA Institution Identifier, which also forms digits 5 to 8 of the nine digit routing number (YYYY).
The denominator is also part of the routing number; by adding leading zeroes to make up four digits where necessary (e.g. 212 is written as 0212, 31 is written as 0031, etc.), it forms the first four digits of the routing number (XXXX).
There might also be a fourth element printed to the right of the fraction: this is the bank's branch number. It is not included in the MICR line. It would only be used internally by the bank, e.g. to show where the signature card is located, where to contact the responsible officer in case of an overdraft, etc.
For example, a check from Wachovia Bank in Yardley, PA, has a fraction of 55-2/212 and a routing number of 021200025. The prefix (55) no longer has any relevance, but from the remainder of the fraction, the first 8 digits of the routing number (02120002) can be determined, and the check digit (the last digit, 5 in this example) can be calculated by using the check digit formula (thus giving 021200025).
This table is up to date as of 2009. One weakness of the current routing table arrangement is that Alaska, American Samoa, Guam, Hawaii, Puerto Rico and the US Virgin Islands share the same routing code.
|1||New York, NY|
|4||St. Louis, MO|
|11||San Francisco, CA|
|14||New Orleans, LA|
|16||Los Angeles, CA|
|18||Kansas City, MO|
|22||St. Paul, MN|
|30||San Antonio, TX|
|31||Salt Lake City, UT|
|33||Des Moines, IA|
|36||St. Joseph, MO|
|37||Fort Worth, TX|
|39||Oklahoma City, OK|
|41||Sioux City, IA|
|47||Cedar Rapids, IA|
|59||Alaska, American Samoa, Guam, Hawaii, Puerto Rico, Virgin Islands|
Canadian transit numbers are regulated by the Canadian Payments Association. A number has the following form:
where XXXXX is a Branch Number, and YYY is an Institution Number. The dash between the branch number and the institution number is an integral part of the transit number. This format is only valid for paper-type transactions such as cheques. For Electronic Fund Transactions (EFT) the current format is a leading zero, the institution number, then the branch number all with no dashes. For example if a cheque reads XXXXX-YYY, the corresponding EFT code would be 0YYYXXXXX.
In a Canadian bank transit number, the last digit of the branch number, with few exceptions, indicates the geographical location of the branch.
Branch numbers ending with:
For example, the number 58876-004 indicates that the associated account is held at an Eastern Ontario branch of The Toronto-Dominion Bank (58876 is the transit number, 5887 is the branch number and 004 is the institution number).
The Canadian Payments Association maintains the Financial Institutions File (FIF) as well as the Financial Institutions Branch Directory (FIBD). The FIF and the FIBD identify routing numbers and addresses for branches of all Canadian financial institutions (whether they have a physical location or a virtual location).
The FIF, which is updated weekly, is a fee-based subscription service that enables its subscribers to validate routing information and to upload the information in a variety of business applications. More details, including available formats and pricing can be found here: cdnpay.ca
The Financial Institutions Branch Directory, also updated weekly, contains the same information found in the FIF and is available free of charge. It is recommended for occasional reference as it cannot be uploaded into business applications and doesn't offer the same validation features as the FIF. The FIBD is accessible at cdnpay.ca.
Canada has similar but different transaction routing structures