ABA numbers are nine-digit codes that identify which bank holds your account

An ABA number (also called a routing number) is a nine-digit code assigned to a specific bank branch by the American Bankers Association. When you send money to someone else's account—whether by wire transfer, ACH payment, or check—the ABA number tells the sending bank exactly which institution and branch should receive the funds. Without it, the money has no address.

Every bank in the United States has at least one ABA number. Large banks with many branches may have different ABA numbers for different regions or departments. Credit unions and other financial institutions that move money through the banking system also have ABA numbers. The number itself is not secret; you can find your bank's ABA number on your checks, your bank's website, or by calling the bank directly.

The ABA number is different from your account number. Your account number identifies you within your bank. The ABA number identifies the bank itself. Together, they form the complete routing information needed to move money between institutions.

Key Takeaways

  • An ABA number is a nine-digit code that identifies a specific bank or credit union in the U.S. banking system.
  • You need the ABA number of the receiving bank when you send a wire transfer, set up an ACH payment, or deposit a check to someone else's account.
  • Your ABA number appears on the bottom left of your checks and is available from your bank's website or customer service.
  • The ABA number works alongside your account number; the ABA identifies the bank, while the account number identifies you within that bank.

How the ABA number is structured

The nine digits of an ABA number follow a specific pattern. The first four digits identify the Federal Reserve district and the bank itself. The next four digits identify the specific branch or processing center. The final digit is a check digit—a mathematical verification that the number is valid and was entered correctly.

You do not need to understand the internal structure to use an ABA number. What matters is that the number is correct and complete. A single wrong digit will send your money to the wrong place or cause the transfer to fail. When you are entering an ABA number, double-check it against your bank's official source.

Where to find your bank's 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. The next set of numbers is your account number.

If you do not have checks, your bank's website usually displays the ABA number in the account information or settings section. You can also call your bank's customer service line and ask for the ABA number associated with your account. Some banks list different ABA numbers for different types of transactions (wire transfers versus ACH payments), so confirm which one you need for your specific transfer.

When you need to provide an ABA number

You provide an ABA number whenever someone outside your bank needs to send money to your account. This includes wire transfers from another bank, ACH payments from an employer or vendor, or direct deposits. If you are setting up automatic bill payments from your bank account, you may need to provide the ABA number to the company receiving the payment.

You also need the ABA number of the receiving bank when you are the one sending money. If you want to wire funds to someone else's account at a different bank, you must provide that bank's ABA number along with the recipient's account number. The same applies if you are setting up a transfer between your own accounts at two different banks.

Checks do not require you to manually enter an ABA number—the number is printed on the check and read electronically during processing. However, for any electronic transfer, you will need to enter the ABA number by hand or through a form.

ABA numbers versus SWIFT codes and IBAN numbers

ABA numbers work only within the United States. If you are sending money to a bank account outside the U.S., you will need a different routing system. International transfers use SWIFT codes (also called BIC codes), which identify banks worldwide. Some countries also use IBAN numbers (International Bank Account Numbers), which include country information and additional account details in a single code.

A U.S. bank may have both an ABA number and a SWIFT code. The ABA number handles domestic transfers; the SWIFT code handles international ones. If you are sending money abroad, ask your bank which code to use for the destination country.

What happens when an ABA number is wrong

If you enter an incorrect ABA number, the transfer may fail before it is sent, or it may be sent to the wrong bank. Some banks will reject the transfer when ready if the ABA number does not match their records. Others may send the money to the wrong institution, and it can take days or weeks to trace and recover it.

If you realize you have entered the wrong ABA number after sending a transfer, contact your bank when ready. Do not wait. Your bank can sometimes intercept the transfer before it reaches the wrong institution. The sooner you report the error, the better the chance of recovery. If the money has already been received by the wrong bank, you may need to contact that bank directly or work through your bank to retrieve the funds.

ABA numbers and account security

Your ABA number is not sensitive information in the way your account number or PIN is. Banks publish ABA numbers publicly, and they appear on every check you write. Sharing your ABA number alone does not put your account at risk.

However, you should not share your full banking information (ABA number plus account number) with anyone you do not trust. Someone with both pieces of information can set up ACH payments from your account or attempt transfers without your permission. If you are providing banking details to a new vendor or service, verify that the company is legitimate before you share anything.

Frequently Asked Questions

Is the ABA number the same as the routing number?

Yes. ABA number and routing number are the same thing. The term "routing number" is more common in everyday banking, while "ABA number" is the formal name used by the banking industry. Both refer to the nine-digit code that directs money to the correct bank.

Can I use the same ABA number for wire transfers and ACH payments?

Usually yes, but not always. Most banks use one ABA number for all transaction types. However, some large banks maintain separate ABA numbers for wire transfers and ACH payments. Check with your bank to confirm which number to use for your specific transaction type.

What if my bank has multiple branches—do they all have the same ABA number?

Not necessarily. Large banks often assign different ABA numbers to different branches or regions. The ABA number on your checks corresponds to the branch where your account is held. If you move branches or open an account at a different location, your ABA number may change.

Do credit unions have ABA numbers?

Yes. Credit unions participate in the same routing system as banks and have ABA numbers assigned to them. You can find your credit union's ABA number the same way you would find a bank's—on your checks, through their website, or by calling customer service.

Can someone steal money from my account if they have my ABA number and account number?

Potentially yes. With both pieces of information, someone could attempt to set up unauthorized ACH payments or transfers from your account. This is why you should only share your full banking details with trusted sources. Monitor your account regularly for unauthorized activity and report any suspicious transactions to your bank when ready.