ACH authorizations are the responsibility of the Originator to obtain from the person they are creating ACH debits/credits for. Unless your bank is the originator, it is not your responsibility.
you will be required to send NOCs for any existing ACH transactions that try to come to the old account to notify the originator of the new account number. depending on your ACH software, you should be able to put an account swap in place so that your bank continues to apply the incorrect account numbered item to the new account, even if the originator has yet to act on the NOC.
you should also notify your clients to contact the originators to let them know that the account details have changed, many originators, specifically utility companies, will not act on NOCs unless they have confirmed with the account holder as well.
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