What Is an ACH NOC (Notification of Change)?

An ACH Notification of Change (NOC), is a type of ACH exception. It is a message from a receiving bank (RDFI) that lets the originator of a transaction know that something in the transaction was incorrect and needs to be changed going foward. Unlike an ACH return which indicates the original transaction failed to post, an NOC indicates that the transaction did post but future attempts may fail if the corrections are not made.

When Do You Receive an NOC?

NOCs are generated by the receiving bank when:

• An account number has changed

• The account type was incorrect (for example, checking instead of savings)

• A routing number has been updated due to a merger

• And a few other uncommon reasons

  
  

For example: If you sent a vendor payment to a routing number that’s been replaced, the payment might go through, but the receiving bank will issue an NOC with the new routing number for future use.

Common NOC Codes

Here are some common NOC (COR) codes and what they mean:

Code	Description	What It Means
C01	Incorrect account number	Use updated account number
C02	Incorrect transit/routing number	Use updated routing number
C03	Incorrect account number and routing	Use both updated values
C05	Incorrect transaction code	Use correct ACH entry type (e.g., checking vs. savings)

Each NOC will include one or more corrected value.

Tip: ACH Pro automatically parses NOCs provided by your bank and provides clear instructions for how to resolve them.

What Happens If You Ignore an NOC?

Failing to update future transactions can lead to:

• Future returns when the correction becomes mandatory

• Bank compliance issues for violating NACHA rules

• Delayed payments or disruptions

  
  

Banks track your compliance with NOC corrections. Consistently ignoring them may flag you as a higher-risk originator.

How ACH Pro Helps Manage NOCs

ACH Pro can help you manage and prevent NOCs by:

• Validating routing numbers

• Parsing NOCs and providing clear resolution instructions

• Updating recipient information

• Generating compliant NACHA files so account numbers and types are correctly formatted

Final Thoughts

ACH NOCs are a critical but often overlooked part of ACH processing. They keep payment data accurate across a rapidly changing financial landscape.

If you receive one, don’t ignore it — update your records promptly to avoid future headaches and consider using a tool like ACH Pro to simplify how you manage payments, NOCs, and compliance.

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