An ABA number is a nine-digit code that identifies which bank holds your account

The ABA number (also called a routing number) tells the banking system which specific bank to send money to when you receive a transfer or pay a bill. It is not tied to your individual account — it identifies the bank itself. Every bank in the United States has one, and many banks have more than one if they operate multiple processing centers or acquired other banks.

The name comes from the American Bankers Association, the organization that originally assigned these codes in the 1910s. The system still works the same way today: when money moves between banks, the ABA number is how the sending bank knows where to route it.

Key Takeaways

  • An ABA number is a nine-digit code that identifies your bank, not your individual account.
  • You need the ABA number when setting up direct deposit, paying bills by check or bank transfer, or receiving money from another bank.
  • Your ABA number appears on the bottom left of your checks, and you can also find it on your bank's website or by calling customer service.
  • The same bank may have different ABA numbers for different branches or processing centers, so always use the one your bank gives you for the specific transaction.

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 — the first nine digits are your ABA number. The next set of digits is your account number, and the final set is the check number.

If you do not have checks, log into your bank's website or mobile app and look for account details or routing information. Most banks list it clearly. You can also call your bank's customer service line and ask for your routing number — they will give it to you when ready.

Some banks display different ABA numbers depending on how you are sending money. For example, the ABA number for a wire transfer might differ from the one for an ACH transfer (a slower electronic transfer used for direct deposit and bill pay). Always use the number your bank specifies for the type of transfer you are making.

When you need to provide your ABA number

You will need your ABA number whenever money is moving from another bank into yours. The most common situations are setting up direct deposit for your paycheck, receiving a wire transfer, or having someone pay you through a bank transfer app.

You also need it when you are sending money out of your account to another bank — for example, when you set up automatic bill payments or transfer money to a friend's account. In both cases, the ABA number tells the banking system which institution to route the money to.

If you are writing a check, you do not need to do anything — your ABA number is already printed on it. But if someone is paying you by electronic transfer and asks for your routing number, that is what they are asking for.

How the ABA number works in a transfer

When you set up a direct deposit, your employer's payroll system uses your ABA number and account number to send your paycheck to the right place. The sending bank reads the ABA number, looks up your bank in its routing database, and sends the funds there. Your bank then uses your account number to deposit the money into your specific account.

The same process happens with bill payments, peer-to-peer transfers, and wire transfers. The ABA number is the address; your account number is the apartment. Without the correct ABA number, the money goes to the wrong bank and the transfer fails or gets delayed while the banks sort it out.

This is why it matters that you use the correct ABA number for the type of transfer. A wire transfer and an ACH transfer (used for direct deposit) may route through different processing centers at the same bank, so they can have different ABA numbers. Using the wrong one will not send your money to a competitor — it will just slow things down or cause the transfer to bounce back.

ABA numbers and bank mergers

When one bank buys another, the acquired bank sometimes keeps its original ABA number for a period of time, or it gets assigned a new one. This can create confusion if you have old checks or records from before the merger.

If your bank was acquired and you are unsure which ABA number to use, ask your bank directly. They will tell you which number is current for your account. Old checks with the previous ABA number will still work because the banking system can usually route them correctly, but for new transfers it is safer to use the current number.

ABA numbers versus SWIFT codes and IBAN numbers

The ABA number works only for transfers within the United States. If you are sending or receiving money internationally, you will need different codes. A SWIFT code identifies a bank globally and is used for wire transfers between countries. An IBAN (International Bank Account Number) is used in Europe and some other regions to identify both the bank and the individual account.

For domestic transfers — money moving between U.S. banks — the ABA number is all you need. Your bank will ask for it along with your account number, and that is sufficient.

What happens if you give the wrong ABA number

If you provide an incorrect ABA number, the transfer usually fails before any money leaves your account. The sending bank's system will not recognize the number and will reject the transaction, sending it back to the sender with an error message.

In rare cases, money sent to the wrong ABA number might go to a different bank. That bank will see that the account number does not match any of their accounts and will return the funds to the sending bank. The process can take several business days, and the sender may see the money temporarily leave their account before it comes back.

This is why it is worth double-checking the ABA number before you set up a new direct deposit or recurring transfer. Once it is set up correctly, it stays the same for future payments.

Frequently Asked Questions

Is my ABA number the same as my account number?

No. Your ABA number identifies your bank; your account number identifies your specific account at that bank. You need both for transfers. The ABA number appears first on a check, followed by your account number.

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

Yes. If you have a checking account and a savings account at the same bank, they share the same ABA number. The account number is what distinguishes them. However, if your bank has multiple processing centers, different accounts might use different ABA numbers — ask your bank to be sure.

Do I need my ABA number to receive a check?

No. Checks already have the ABA number printed on them. You only need to provide your ABA number when someone is sending you money electronically or when you are setting up automatic payments.

What if my bank does not have a website and I cannot find my ABA number?

Call your bank's customer service number, which is usually on the back of your debit card or on any statements they send you. They can tell you your ABA number over the phone in less than a minute.

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

Not with just the ABA number alone. They would also need your account number, and even then they cannot withdraw money — they can only send money to your account. To actually take money out, they would need access to your online banking login or your debit card.