Routing Transit Number Explained: Find Yours and Understand Its Use

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A routing transit number (RTN) is a nine-digit code that identifies a U.S. bank or credit union when money moves electronically or a check is processed. It tells the payment system which institution holds an account. It does not identify the account itself; that is the job of your account number. “Routing number,” “routing transit number,” “ABA number” and, in U.S. usage, “transit number” all refer to the same code.

What a routing transit number does

When you set up direct deposit, pay a bill or receive a wire, the sender needs to know where your account is held and which account it is. The routing number answers the first question: clearinghouses, the Federal Reserve and the banks on each side read it to direct the payment or check to the correct institution.

Only institutions eligible to hold an account at a Federal Reserve Bank are assigned routing numbers. LexisNexis Risk Solutions acts as the official registrar for the ABA, and a newly organized bank or credit union must apply for a number before it can take part in check clearing and electronic payments.

The ABA introduced routing numbers in 1910 to sort paper checks, and the same codes were later adopted to identify banks in ACH transfers, wires and online banking. Standardized numbers, machine-readable printing and electronic verification also made it harder for fraudsters to falsify the routing number on a check.

How the nine digits are structured

Its digits follow a fixed layout:

• Digits 1 to 4: Federal Reserve routing symbol. The first two digits point to the Federal Reserve district associated with the institution. Commercial banks use 01 to 12, one code for each of the twelve districts. Thrift institutions use the same district numbers plus 20 (21 to 32). The third digit identifies the Federal Reserve office that serves the bank, and the fourth relates to the institution’s location within the district. Because of this scheme, a U.S. routing number starts with 0, 1, 2 or 3.
• Digits 5 to 8: ABA institution identifier. These identify the specific bank within that Federal Reserve area.
• Digit 9: check digit. This digit is calculated from the first eight so that software can tell whether the full number was entered correctly.

Worked example: the check digit formula

The ninth digit must satisfy a weighted checksum. Multiply each digit by the weights 3, 7, 1, repeating across all nine positions, and add the results. For a valid routing number, the total is a multiple of 10:

3 × (d1 + d4 + d7) + 7 × (d2 + d5 + d8) + 1 × (d3 + d6 + d9) = a multiple of 10

Hypothetical example (not a real bank’s number): take the first eight digits 1 2 3 4 5 6 7 8.

• 3 × (1 + 4 + 7) = 3 × 12 = 36
• 7 × (2 + 5 + 8) = 7 × 15 = 105
• 1 × (3 + 6) = 9 so far, before adding d9

The subtotal is 36 + 105 + 9 = 150. That is already a multiple of 10, so the check digit d9 must be 0, giving 123456780.

If someone swaps two adjacent digits and types 213456780, the first group becomes 3 × (2 + 4 + 7) = 39 and the second becomes 7 × (1 + 5 + 8) = 98. The total is 39 + 98 + 9 = 146, which is not a multiple of 10. A payment form running this check would reject the number before the payment is sent.

Where to find your routing number

On a check. The bottom of a check carries a line of numbers printed in magnetic ink (the MICR line) so machines can read it. The nine digits at the far left, set off by special bracket-like symbols, are the routing number. Next come your account number and the check number. The check number on the bottom line matches the number printed in the upper right corner, which makes it easy to tell apart from the other two groups.

Some checks also show a fractional routing symbol, sometimes called the fractional bank number, near the top. It is an older way of printing the same routing information, written as a fraction.

In online or mobile banking. Most banking portals and apps show the routing number on the account details screen, usually next to the account number. Many banks also list it on statements and on direct deposit forms you can download.

From the bank. Banks often publish their routing numbers on their websites, and customer service can confirm the right number for your account. Asking the bank is the safest route when it lists more than one number.

How routing numbers are used

• Direct deposit. Employers and government agencies, including the IRS for tax refunds, use your routing and account numbers to deposit funds electronically instead of mailing a check.
• ACH payments. Automatic bill payments, transfers between your own accounts at different banks, and linking a bank account to services such as PayPal or Venmo all rely on the routing number to reach your institution.
• Wire transfers. A domestic wire sends payment instructions between banks, including the amount and the recipient’s account details. The routing number makes sure they reach the correct receiving bank.
• Check processing. When you deposit a check, your bank reads the routing number from the MICR line to know which institution to collect the funds from.

A wrong but valid routing number can send a payment to a different bank, where it may be rejected or delayed while the institutions sort it out. That is why the number entered on a deposit or transfer form should be copied from your bank’s own materials rather than from memory.

Routing number vs. other banking codes

Routing number vs. transit number. In the United States these are the same thing. In Canada, a transit number is a five-digit code for a specific bank branch, used together with a three-digit institution number. Canadian electronic payments combine them into a nine-digit routing number (a leading 0, then the institution number, then the branch transit number). If a form asks for a transit number, the country of the account determines what it means.

Routing number vs. account number. The routing number is shared by every customer of the bank (or of that bank’s region or payment type) and is always nine digits. The account number belongs to you alone, and its length varies from bank to bank.

Routing number vs. SWIFT code. A SWIFT code, also called a BIC, is an 8- or 11-character alphanumeric code that identifies a bank in international transfers. A U.S. bank receiving a wire from abroad is identified by its SWIFT code, not its RTN.

Routing number vs. IBAN. An International Bank Account Number is a long alphanumeric code, up to 34 characters, that bundles the country, bank, branch and account number into one string. It is used mainly for international payments in countries that have adopted it. U.S. accounts do not have IBANs.

Limitations and practical points

One bank, several numbers. A single institution may use different routing numbers for ACH transfers, paper checks and wire transfers. Large banks may also assign numbers by the state or region where the account was opened, and banks that have merged can keep more than one number. The number printed on your checks is not always the one your bank wants used for incoming wires.

It is not secret, but it is not harmless. Routing numbers are public information printed on every check. Paired with your account number, though, they can be used to set up electronic debits or create counterfeit checks. Share both numbers only with parties you have a reason to pay or be paid by.

FAQs

The Bottom Line

Anyone setting up direct deposit, linking a bank account to a payment app or receiving a wire needs the correct routing number. Copy it from your bank's own materials, and ask the bank when it lists more than one number, since a wrong but valid number can delay a payment. Share your routing and account numbers together only with parties you have a reason to pay or be paid by.