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
The RTN number is derived from the bank's transit number
originated by the American Bankers Association, which
designed it in 1910
ABA number management
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; the Fed requires banks to phase
these out (to a single surviving RTN per state, or fewer)
within about 18 months. Once support for such "old paper" is
dropped, customer's checks will "bounce" and be returned
unpaid to the merchant or originator.
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 call 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 a 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.
Routing number format
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
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 SymbolThe 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.[
First two digitsThe 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:
|Federal Reserve Bank
Third and fourth digitsThe 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
Check digitThe 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 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 fraction form looks like a fraction, with a numerator and a
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. The 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.
||New York, NY
||St. Louis, MO
||San Francisco, CA
||New Orleans, LA
||Los Angeles, CA
||Kansas City, MO
||St. Paul, MN
||San Antonio, TX
||Salt Lake City, UT
||Des Moines, IA
||St. Joseph, MO
||Fort Worth, TX
||Oklahoma City, OK
||Sioux City, IA
||Cedar Rapids, IA
Samoa, Guam, Hawaii, Puerto Rico, Virgin Islands
List of SWIFT Codes