Key Difference: The ABA Routing Number is a nine-digit number that is located on the check, it is also known as the Routing Transit Number (RTN). The Automated Clearing House (ACH) Routing Number is also a nine-digit number, similar to the ABA Routing Number. In many cases, the ABA and ACH number are the same.

There are various ways that money can be transferred to and from your bank account. It could be done via checks, demand drafts, wire transfer, etc. However, due to the growing amount of the number of banks, the American Banking Association (ABA) has created a numerical system in order to differentiate banks as an individual entity. In order to be a running bank, you need these certain registry numbers that are provided by the ABA. These numbers include the ABA Routing Number and the ACH Routing Number. The numbers are designed to make the transfer of money easy and effective.

The ABA Routing Number is a number that is located on the check, it is also known as the Routing Transit Number (RTN). This is a nine-digit code that is located on the bottom left hand corner of the check and will be preceded and followed and followed by the ‘⑆’ transit character. Similar to the ABA Number, a number that is assigned to identify the bank, this code identifies the unique number of the financial institution from which the check is drawn and the code of the Federal Reserve Bank that serves this particular financial institution.

The first two digits of the routing number must be in the ranges 00 through 12, 21 through 32, 61 through 72, or 80. The first two digits correspond to the 12 Federal Reserve Banks located in various different states. The third digit corresponds to the Federal Reserve check processing center originally assigned to the bank, while the fourth digit is "0" if the bank is located in the Federal Reserve city proper, and otherwise is 1–9, according to which state in the Federal Reserve district it is. Routing numbers are also more commonly being used for electronic transfers, bill payments, online banking and automated transfers.

The Automated Clearing House (ACH) Routing Number is a number that is similar to the ABA Routing Number. It is also a nine-digit number. The only difference between the two is that the ACH Number is used for digital transactions such as direct deposit, or direct payment. Even in this case, The ABA Routing Number and the ACH Routing Number could be the same. In case it is the same, the routing number on the left, bottom corner of the check can be used to provide for digital transactions. However, it if is different, one would have to call the bank and acquire the unique ACH Number in order to start online transactions. The number can also be available on the bank’s website.

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