# Routing transit number

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.

The RTN is also used by Federal Reserve Banks to process Fedwire funds transfers, and by the Automated Clearing House to process direct deposits, bill payments, and other such automated transfers.

The RTN number is derived from the bank's transit number originated by the American Bankers Association, which designed it in 1910.[1]

## ABA number management

Since 1911, the American Bankers Association has assigned transit numbers through a series of registrars, currently Accuity.[2] 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.[3] 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.[4] 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.

## Routing number format

A check showing the fraction form (top middle-right, 11-3167/1210 plus branch number 01) and MICR form (bottom left, 129131673) of the transit number.

The ABA transit number appears in two forms on a standard check – the fraction form and the MICR (magnetic ink character recognition) form.[1] 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. 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 Dallas,
• 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 handlings.

## MICR Routing number format

The MICR routing number consists of 9 digits:

XXXXYYYYC

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

### Federal Reserve Routing Number

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.[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:

Primary
(01–12)
Thrift
(+20)
Electronic
(+60)
Federal Reserve Bank
012161Boston
022262New York
042464Cleveland
052565Richmond
062666Atlanta
072767Chicago
082868St. Louis
092969Minneapolis
103070Kansas City
113171Dallas
123272San 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.[4]

### Check digit

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:[1]

$3 (d_1 + d_4 + d_7) + 7 (d_2 + d_5 + d_8) + (d_3 + d_6 + d_9) \mod 10 = 0.\,$
(Mod or modulo is the remainder of a division operation.)

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 $5 \cdot 0 = 5 \cdot 2 = 5 \cdot 4 = 5 \cdot 6 = 5 \cdot 8 = 0 \mod 10$), 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.[citation needed]

As an example, consider 111000025 (which is a valid routing number of Bank of America in Virginia). Applying the formula, we get:

$3 (1+0+0) + 7 (1+0+2) + (1+0+5) \mod 10 = 0.\,$

The following formula can be used to generate the ninth digit in the checksum:

$d_9 = 7 (d_1 + d_4 + d_7) + 3 (d_2 + d_5 + d_8) + 9 (d_3 + d_6) \mod 10.\,$

This is just moving all terms other than $d_9$ to the right hand side of the equation, which inverts the coefficients with respect to 10 ($3 \mapsto (10-3) = 7; 7 \mapsto (10-7) = 3; 1 \mapsto (10-1) = 9$).

Following the above example for the Bank of America routing number 111000025,

$7 (1+0+0) + 3 (1+0+2) + 9 (1+0) = 25 \mod 10 = 5.\,$

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[0] + d[3] + d[6]) +              3 * (d[1] + d[4] + d[7]) +              9 * (d[2] + d[5])            ) % 10 print(d[8] == checksum)

### Routing symbol

The symbol that delimits a routing transit number is the MICR E-13B transit character (Unicode value U+2446): ⑆

If your computer cannot display this character, it may be seen here.

## Fraction form

The fraction form looks like a fraction, with a numerator and a denominator.

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).

### ABA Prefix Table

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.

prefixlocation
1New York, NY
2Chicago, IL
4St. Louis, MO
5Boston, MA
6Cleveland, OH
7Baltimore, MD
8Pittsburgh, PA
9Detroit, MI
10Buffalo, NY
11San Francisco, CA
12Milwaukee, WI
13Cincinnati, OH
14New Orleans, LA
15Washington D.C.
16Los Angeles, CA
17Minneapolis, MN
18Kansas City, MO
19Seattle, WA
20Indianapolis, IN
21Louisville, KY
22St. Paul, MN
23Denver, CO
24Portland, OR
25Columbus, OH
26Memphis, TN
27Omaha, NE
28Spokane, WA
29Albany, NY
30San Antonio, TX
31Salt Lake City, UT
32Dallas, TX
33Des Moines, IA
34Tacoma, WA
35Houston, TX
36St. Joseph, MO
37Fort Worth, TX
38Savannah, GA
39Oklahoma City, OK
40Wichita, KS
41Sioux City, IA
42Pueblo, CO
43Lincoln, NE
44Topeka, KS
45Dubuque, IA
46Galveston, TX
47Cedar Rapids, IA
48Waco, TX
49Muskogee, OK
50New York
51Connecticut
52Maine
53Massachusetts
54New Hampshire
55New Jersey
56Ohio
57Rhode Island
58Vermont
59Alaska, American Samoa, Guam, Hawaii, Puerto Rico, Virgin Islands
60Pennsylvania
61Alabama
62Delaware
63Florida
64Georgia
65Maryland
66North Carolina
67South Carolina
68Virginia
69West Virginia
70Illinois
71Indiana
72Iowa
73Kentucky
74Michigan
75Minnesota
77North Dakota
78South Dakota
79Wisconsin
80Missouri
81Arkansas
83Kansas
84Louisiana
85Mississippi
86Oklahoma
87Tennessee
88Texas
90California
91Arizona
92Idaho
93Montana
95New Mexico
96Oregon
97Utah
98Washington
99Wyoming
101Assigned

Canadian transit numbers are regulated by the Canadian Payments Association. A number has the following form:

XXXXX-YYY

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.

As a general rule, Bank institution numbers start with 0, 2, 3, or 6, Credit Union and Caisse Populaire institution numbers start with 8, and Trust Company institution numbers with 5.

Examples:

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.