Is there any issue providing the C5A notice to business account holders who get a returned substitute check?

229.57 applies to consumers. If you provide the C5A notice referenced in this section to business account holders, it probably won't hurt as long you do what the disclosure says you will do (and provide the customer the rights the disclosure says they have). That said, this is more of a legal question (contract issue) than a compliance question so you may want to run it by legal counsel.

If the original notice has a mailing address with a PO BOX that is to be discontinued, would an updated notice need to go out to the customer if our statement has a notice on the back with the new address for any error resolution?

You deliver actual substitute checks with your account statements?

No, we do not.

Then I am confused as to why you would be giving a consumer such a disclosure, as you only have to provide it when delivering substitute checks to them. If you deliver substitute checks during the returned check process, that disclosure must accompany that delivery every time.

Delivering substitute checks to customers may have been done in the early years of Check 21, but the virtually complete conversion to electronic check clearing has all but eliminated the practice.