Routing Number vs. Account Number: Which Is Which on a Check

Look at the bottom edge of a paper check. Three groups of digits, left to right: routing number, account number, check number.

The routing number is always nine digits. The account number is whatever length your bank uses, commonly between eight and twelve. The check number matches the number printed in the top-right corner, which is the quickest way to work out which group is which.

The routing number, formally the ABA routing transit number, was created in 1910 to sort paper cheques by the bank that had to pay them. The first four digits encode the Federal Reserve district and office that used to process them, the next four identify the institution, and the ninth is a check digit calculated from the other eight.

That last digit is why a mistyped routing number is usually rejected rather than misrouted: the arithmetic no longer adds up, and the system refuses it before the money moves. Your account number has no such protection, which is the reason a typo there is far more dangerous.

The large national banks kept the routing numbers of every bank they ever merged with, so yours generally depends on the state where the account was opened rather than where you live now.

There is also a second split. Many banks publish one routing number for ACH transfers — direct deposit, bill payment, transfers between banks — and a different one for domestic wires. Sending a wire to the ACH number is a common and slow mistake.

The reliable answer is the one your own bank gives you in its app or on your statement, filtered by transfer type. If you need to verify a routing number that somebody else gave you, the Federal Reserve publishes the official participant directory.

Handing over both numbers lets someone deposit money into your account. It also lets them take money out by ACH debit, which is exactly how a fraudulent payment is set up.

Give them to an employer for payroll, to a government agency for a refund or benefit, to a lender for autopay, or to yourself when linking accounts you own. Do not give them to a stranger who contacted you first, whatever the reason offered.

If an unauthorised debit does appear, Regulation E gives you an error-resolution right at the bank that holds your account, and the clock on it starts when the statement showing the transfer is sent. Reporting fast is what keeps your liability at the lowest tier.