More information can be found in Chapter 13 “ODFI Audit Requirements and Rules Compliance” found on OG52 of the NACHA Operating Rules. The first sentence in Chapter 13 states:
"All ODFIs, Third Party Service Providers performing a function of ACH processing on behalf of those ODFIs, and Third Party Senders must perform an annual audit to determine compliance with all provisions of the NACHA Operating Rules."
Third Party Service Providers and Senders are very well defined in the NACHA rules and the definition does not include Originators. Our reading of this opening statement would indicate the scope of the credit union's audit would not expand your responsibilities into the ODFI Articles of the rule book. However, your auditor may have a differing opinion so we encourage you to understand this section and get further professional guidance if you have questions.