<P> 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 . </P> <P> 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 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 . </P> <P> 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 . </P> <P> Incoming international wire transfers also use the SWIFT code - a system administered by the Society for Worldwide Interbank Financial Telecommunication (SWIFT). The code is often referred to as "SWIFT - BIC, BIC code, SWIFT ID or SWIFT code". Please see ISO 9362 . In addition, European financial institutions use an IBAN code . </P>

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