The ABA introduced routing numbers in 1910. It enables banks and businesses to identify the financial institution holding a particular account. That reduces the time required to process the check. As the financial industry has changed, the ABA has kept up, adapting to the creation of the Federal Reserve and the use of Magnetic Ink Character Recognition. MICR is a system for printing checks with magnetic ink, making it easier to scan routing and check numbers mechanically.
Routing Number History
The ABA System
Only federally chartered institutions eligible to have an account with the Federal Reserve receive ABA numbers. A new bank must apply to Accuity, the routing number registrar, for its number. Accuity also publishes a semi-annual guide to routing numbers banks can use to identify the bank that a given check traces back to. The guide also includes the last five years of retired numbers, such as from banks that have had to close.
A given bank may have branches spread out across multiple states. They don't all have the same routing number. Bank of America, for example, says its banks in different states have different ABA numbers. In some states, different regions have different numbers as well. There also are different routing numbers for different types of accounts and transactions. U.S. Bank notes that its savings accounts, checking accounts and IRAs may all have different routing numbers.
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Need to Know
If someone pays you with a check, you don't need to worry about routing numbers. You can drop it off at your bank and let the staff look up the number and process the payment. If you're making a wire transfer or paying bills online, you may be asked for the routing number. The routing number for these transactions is usually different from the one on your checks, so check with the bank to make sure you're sending the funds to the right place.