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What is an ABA Number? How It Works & Where to Find One


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ABA numbers identify financial institutions by routing number, account number, and check number. ABA numbers are used for electronic bank-to-bank account transfers, including paper and electronic check processing, ACH transactions, and wire transfers through the Fedwire system.

We explain the meaning of the ABA number and how it’s used through a series of FAQs. 

What is an ABA Number? 

An ABA number is the three sets of numbers on the bottom of paper checks, from left to right, that identify (1) the financial institution via a nine-digit routing number from the American Bankers Association, (2) bank account number, and (3) check number. The fractional routing number on the top of the check is a backup ABA number.

Are an ABA Number and Routing Number the Same?

An ABA number is also referred to as the bank routing number. For ACH and wire transfers, the routing number may be different. Check with your bank to verify the correct routing number to use for a transaction. 

How Do I Obtain an ABA Number? 

If your financial institution is federally or state-chartered with eligibility to maintain an account at a Federal Reserve Bank, you can submit an application and an application fee to obtain an ABA number through LexisNexis Risk Solutions. LexisNexis Risk Solutions became the official ABA number registrar after its merger with Accuity in February 2021.

How Do I Find My Bank’s ABA Number? 

You can find your bank’s ABA number, including the nine-digit routing number, in the left-most position on the bottom of your check, printed with machine-readable magnetic ink (MICR). To the right of the nine-digit ABA routing number are a bank account number and a check number. 

The (MICR) machine-readable ABA number is printed with magnetic ink on the bottom left of each bank check. A fraction form shows a backup ABA number near the top of the same check, which is a different set of numbers, including the branch number. 

Savings accounts and checking accounts have ABA numbers, which can be printed on deposit slips too.

Some banks use multiple routing numbers for different purposes. For example, the routing number may not be the ABA number shown on your check for domestic wire transfers received or to order paper checks.

ABA numbers aren’t used on a bank-issued debit card that can be used for payment transactions or ATM withdrawals.

Because bank mergers & acquisitions (M&A) transactions can change your financial institution’s ABA number, you can search for your financial institution’s current ABA number on the American Bankers Association ABA Routing Number Lookup page on their website. You can look at your bank’s website or your online banking app to find their routing number. 

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What is an ABA Number Example?

An ABA number is officially called an ABA routing transit number (ABA RTN).

The ABA routing number, a nine-digit number, includes:
• First two numbers: Regional Federal Reserve Bank
• Number three: Check processing center
• Number four:  Federal Reserve District state
• Numbers five through eight: Financial institution identifying number
• Number nine: check digit (checksum character)

This link to U.S. Bank’s Find Your Routing Number web page includes an ABA number visual example.

The fractional ABA number is an eight or nine-digit number that resembles a fraction with a numerator with a hyphen and denominator.

According to BankersOnline.com, the fractional numerator is five digits, and the denominator is three or four digits. The first two digits in the numerator before the hyphen are the City/State Prefix, and the three digits after the hyphen are the ABA Institution Identifier. The three or four digits in the denominator are the Federal Reserve Routing Symbol.  

Is ABA the Same as a Wire Routing Number?

For domestic U.S. bank wire transfers, the recipient’s ABA routing number and bank account number may be used for the wire routing number. For international wire transfers, a SWIFT code, IBAN, or BIC (bank identification code) may be required instead. It’s essential to verify with your bank what nine-digit code to use as the wire routing number.

An IBAN is a standardized international bank account number starting with a two-digit country code. 

Who Uses ABA Numbers, And For What Are They Used? 

Financial institutions (including banks and credit unions), bank customers, and money transfer systems use ABA numbers that include a bank routing number.

ABA numbers are used for check payments clearing, electronic  ACH (Automated Clearing House) transfers between U.S. financial institutions, and some wire transfers. Types of ACH transactions include direct deposit, automatic bill payments, online vendor payments, other B2B payments, and person-to-person payments. 

If you have personal loans, including a mortgage, or a business loan, you’ll need to provide your bank account’s ABA number for the approved loan to receive the money.

ACH and wire transfers are electronic funds transfer (EFT) or electronic payment methods to transfer money between the payer’s and recipient’s bank accounts. ACH payments have less scam and fraud risk than wire transfers. Read more about ACH vs. wire transfer

How are Federal Reserve Banks using ABA Numbers?

The Federal Reserve Check Services offer electronic and paper check products and services, using a check processing center for overnight processing and the Federal Reserve routing system.

Wire transfers go through the Federal Reserve Banks’ Fedwire Funds Service that offers customer support through either The Federal Reserve Bank of Boston or Kansas City, depending on your Federal Reserve District. Fedwire processes same-day wire transfers.

“The Federal Reserve Banks provide the Fedwire Funds Service, a real-time gross settlement system that enables participants to initiate funds transfer that are immediate, final, and irrevocable once processed. Depository institutions and certain other financial institutions that hold an account with a Federal Reserve Bank are eligible to participate in the Fedwire Funds Services.”

What is the Importance of ABA Numbers?

ABA numbers are important because they identify financial institutions for processing payments and making direct deposits. ABA numbers include check routing numbers.

State and federally-chartered U.S. banks and other financial institutions with Federal Reserve Bank accounts are assigned unique ABA numbers for processing checks, electronic payments, and ACH direct deposit. Electronic payments include online banking and mobile banking transactions using ACH and wire transfers.

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