What is ABA code?

A unique number assigned by the American Bankers Association (ABA) that identifies a specific federal or state chartered bank or savings institution. In order to qualify for an ABA transit number, the financial institution must be eligible to hold an account at a Federal Reserve bank. ABA transit numbers are also known as ABA routing numbers, and are used to identify which bank will facilitate the payment of the check.

Investopedia explains 'ABA Transit Number'

The ABA Transit number was originally developed in 1910 to indicate check processing endpoints. Since then, the number's use has increased to include participants in check clearing between banking institutions, automated clearing houses and online banking activities.

The ABA check routing number is usually the first nine digits in the bottom row of numbers on any check. For example, if the bottom row showed 123456789 0100100120: 0123, the ABA routing number would be 123456789.
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