For decades, the business world has used unencrypted electronic mail and fax machines to resolve disputes and transmit images of documents. With ACH processing, such interactions and business documents often contain details necessary to resolve an exception that prevented straight-through processing of an ACH payment, or to process a request or claim regarding an ACH payment. For example, an ODFI might need to provide proof of a consumer’s authorization for an ACH Debit at an RDFI's request, or provide a signed Letter of Indemnity to support a request for the return of an ACH Credit from an RDFI.

Because of security vulnerabilities inherent in the processes associated with communicating to non-authenticated recipients, and in sending and receiving faxes or email to unintended parties, Nacha recommends the use of secure electronic channels as a best practice for sharing information and exchanging documents necessary to resolve ACH exceptions.

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