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

The ABA number, also called a routing number, tells the banking system which financial institution to send money to or pull money from. When you set up a direct deposit, pay a bill by check, or move money between banks, the ABA number is what makes sure the funds reach the right place. Every bank and credit union in the United States has its own ABA number, and many larger institutions have multiple numbers for different regions or branches.

The term "ABA" comes from the American Bankers Association, the organization that originally created and assigned these codes in the 1910s. The system has stayed largely the same for over a century because it works — it is the backbone of how money moves through the U.S. banking system.

Key Takeaways

  • An ABA number is a nine-digit code unique to each bank or credit union, used to route money to the correct financial institution.
  • You need your ABA number whenever you set up direct deposit, arrange automatic bill payments, or transfer money between accounts at different banks.
  • Your ABA number appears on the bottom left of your checks and is also available from your bank's website, app, or customer service line.
  • The ABA number is different from your account number — the ABA identifies your bank, while your account number identifies your specific account within that bank.

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 — the first nine digits printed there make up your ABA number. The next set of digits is your account number.

If you do not have checks handy, log into your bank's website or mobile app and look for account details or routing information. Most banks display the ABA number in the account summary section. You can also call your bank's customer service line and ask for your routing number — they will give it to you over the phone.

Some banks list different ABA numbers for different types of transactions, such as ACH transfers versus wire transfers. If you are setting up a specific type of transfer, ask your bank which ABA number to use for that particular transaction.

Why banks need your ABA number

When you set up direct deposit for your paycheck, your employer needs your ABA number and account number to send the money to the right place. Without the ABA number, the payroll system would not know which bank to contact. The same applies when you arrange automatic bill payments — your utility company or credit card issuer uses the ABA number to pull money from your account on the scheduled date.

Wire transfers also require an ABA number. If you are sending money to someone at a different bank, or receiving a wire transfer, both banks use ABA numbers to confirm the transaction and move the funds. The ABA number acts as an address for your bank within the national banking network.

Even when you transfer money between your own accounts at two different banks, the receiving bank uses the sending bank's ABA number to locate and retrieve the funds. Without this routing system, the banking network would have no way to sort and deliver millions of daily transactions.

ABA number versus account number

These two numbers work together but serve different purposes. Your ABA number identifies your bank — it is the same for everyone who banks at that institution. Your account number is unique to you and identifies your specific account within that bank. Think of the ABA number as the address of the bank building, and your account number as your mailbox inside that building.

When you provide banking information, you usually need to give both numbers. A direct deposit form, for example, will have separate fields for routing number (ABA) and account number. Giving only one without the other is not enough — the system needs both to know where to send the money and whose account to deposit it into.

What happens if you use the wrong ABA number

If you provide an incorrect ABA number, the money will go to the wrong bank. Depending on the type of transaction, the receiving bank may reject the transfer, or it may sit in a holding account while the banks sort out the error. Direct deposits that go to the wrong bank are usually caught and returned to your employer, who will resubmit with the correct information.

Wire transfers with a wrong ABA number are more complicated. The money may reach a different bank, and recovering it can take days or weeks. Always double-check your ABA number before submitting any transfer, especially for large amounts or one-time transactions.

If you have already sent money with an incorrect ABA number, contact your bank immediately. They can sometimes trace the transfer and help retrieve the funds, but the sooner you report the error, the better your chances of recovery.

ABA numbers for different types of institutions

Banks, credit unions, and online banks all have ABA numbers. A credit union's ABA number works the same way as a traditional bank's — it routes money to that specific credit union. Online banks also have ABA numbers, even though they do not have physical branches. When you set up direct deposit or bill pay with an online bank, you will use its ABA number just as you would with any other bank.

Some large banks and credit unions operate multiple branches or regional divisions and may have different ABA numbers for different locations or transaction types. If you are unsure which ABA number to use, your bank's customer service can tell you which one applies to your specific account and the type of transaction you are making.

Frequently Asked Questions

Is my ABA number the same as my routing number?

Yes, ABA number and routing number are the same thing. Both terms refer to the nine-digit code that identifies your bank. You may see them used interchangeably on bank forms and websites.

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

Usually yes, but not always. Most banks use the same ABA number for both types of transfers. However, some larger institutions have different routing numbers for wire transfers versus ACH transfers. Check with your bank or look at the specific form you are filling out — it will usually specify which routing number to use.

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

Not necessarily. When banks merge, the surviving bank may keep both ABA numbers active for a transition period, or it may assign a new ABA number to all accounts. Your bank will notify you if your ABA number changes and provide the new one. Your existing direct deposits and bill payments may need to be updated with the new number.

Do I need to memorize my ABA number?

No. You only need to know where to find it when you need it. Keep a check or a note with your ABA number in a safe place, or simply look it up on your bank's website or app whenever you need to provide it.

Can someone use my ABA number and account number to steal money from my account?

Your ABA number and account number alone are not enough to authorize a withdrawal. However, you should still keep this information private. If someone has both numbers plus other personal information, they could potentially set up unauthorized transfers. If you suspect fraud, contact your bank immediately.