An ABA number is a nine-digit code that identifies the specific bank or credit union where you hold an account

The ABA number tells the financial system which institution to send money to when you receive a transfer, a direct deposit, or a check. It is used alongside your account number to route payments to the right place. The code is also called a routing number or routing transit number (RTN), and the terms are interchangeable — they all refer to the same nine digits.

ABA stands for American Bankers Association, the organization that originally assigned these codes in the 1910s. The system was built to sort paper checks by hand before computers existed, but it remains the standard way to identify banks in the United States today. Every bank and credit union that participates in the U.S. payment system has at least one ABA number, and some large institutions have multiple numbers for different branches or services.

Key Takeaways

  • An ABA number is a nine-digit code unique to your bank or credit union, used to route money to the correct institution.
  • You need your ABA number whenever you set up direct deposit, request a wire transfer, or provide banking details to an employer or service.
  • Your ABA number is printed on the bottom left of your checks, or you can find it by calling your bank or visiting their website.
  • The ABA number identifies only the bank — your account number identifies you within that bank, and both are required for most transfers.

Where to find your ABA number

The easiest place to find your ABA number is on a check from your account. Look at the bottom left corner of the check. You will see a series of numbers: the first nine digits are your ABA number, followed by your account number, then the check number on the right.

If you do not have checks, call your bank's customer service line or log into your online banking portal. Most banks display the routing number in the account details or settings section. You can also search the Federal Reserve's routing number database online by entering your bank's name and state, though this requires knowing which specific branch you use if your bank has multiple locations.

Credit unions use ABA numbers the same way banks do. If you belong to a credit union, the routing number appears on your checks or in your account information online.

How banks use the ABA number to move money

When you receive a direct deposit from your employer, the employer's payroll system uses your ABA number to send the payment to your bank instead of any other bank. The payment travels through the Federal Reserve's network, which sorts transfers by ABA number to may support each one reaches the correct institution. Without the ABA number, the system would not know where to send the money.

The same process happens with wire transfers, ACH transfers (automated clearing house transfers that take one to three business days), and bill payments you set up through your bank. Each time money moves into your account from outside, the sender uses your ABA number to identify your bank. Each time money moves out of your account to another bank, your bank uses the recipient's ABA number to send it to the right place.

The ABA number alone does not identify you — it identifies only the bank. That is why you always need both your ABA number and your account number together. The ABA number says "this money goes to Chase Bank in New York." Your account number says "and specifically to account 123456789 at that branch."

ABA numbers for different types of institutions

Banks, credit unions, and some online-only financial institutions all have ABA numbers. If you bank with a large national bank like Chase, Bank of America, or Wells Fargo, you have one ABA number that works for all your accounts at that bank, regardless of which branch you opened the account at. Some very large banks assign different ABA numbers to different regions or divisions, but you will use the same number for all transfers to your account.

Credit unions also have ABA numbers. If you belong to a credit union, the routing number works the same way as a bank's — it identifies your credit union in the payment system. Online banks and fintech companies that hold FDIC insurance also have ABA numbers, even though they have no physical branches.

If you have accounts at multiple banks, each bank has its own ABA number. You need to use the correct ABA number for whichever bank you are sending money to or receiving money from.

Why the ABA number still matters in a digital world

The ABA routing system is over a century old, but it remains the backbone of how money moves between accounts in the United States. Even though most payments now happen electronically instead of by paper check, the system still uses the same nine-digit code to sort and deliver transfers. The Federal Reserve processes trillions of dollars in transfers every year using ABA numbers.

This means you will encounter your ABA number regularly: when you set up direct deposit at a new job, when you ask your bank to send a wire transfer, when you provide banking details to a service or vendor, or when you move money between your own accounts at different banks. Knowing where to find it and understanding what it does saves you time and prevents delays.

What happens if you use the wrong ABA number

If you provide an incorrect ABA number, the payment will be routed to the wrong bank. Depending on the type of transfer, the money may be returned to the sender, held in a suspense account, or credited to someone else's account at the wrong bank. Direct deposits and ACH transfers that go to the wrong bank are usually caught and returned within one to three business days, but the delay means you might not have access to the money when you expected it.

Wire transfers sent to the wrong ABA number are harder to recover. Once a wire leaves your bank, it is difficult to reverse. If the money lands in another account, you would need to contact that bank and ask them to return it, which can take weeks or may not happen at all if the receiving account holder refuses.

Always double-check the ABA number before you authorize a transfer, especially for wire transfers or large amounts. If you are unsure, call your bank or the recipient's bank to confirm the correct routing number.

Frequently Asked Questions

Is my ABA number the same as my account number?

No. Your ABA number identifies your bank; your account number identifies you within that bank. Both are required for transfers. The ABA number is nine digits and appears first on a check. Your account number is longer and appears after the ABA number.

Can I use the same ABA number for all my accounts at one bank?

Yes. Most banks assign one ABA number to all accounts you hold at that bank, regardless of account type or branch. If you have a checking account and a savings account at the same bank, they share the same routing number.

Do I need my ABA number to send money out of my account?

No. You need the recipient's ABA number and account number. Your bank already knows its own routing number. When you set up a transfer or bill payment, you provide the recipient's information, and your bank uses that to send the money to the correct place.

What if my bank merged with another bank — does my ABA number change?

Sometimes. If your bank is acquired by another bank, the acquiring bank may assign a new ABA number to your account, or it may keep the old one. Your bank will notify you if this happens and provide the new routing number. Any direct deposits or automatic payments you have set up will need to be updated with the new number.

Can I look up someone else's ABA number?

You can search for a bank's ABA number using the Federal Reserve's routing number database if you know the bank name and state. However, you cannot determine which specific account belongs to which person using only a routing number — that information is private to the account holder and their bank.