Not to pile on, but...
in addition to everything above, you need to send NOCs on every single item received, not just federal. Be aware that because of fraud and such, many utility companies will not act on a NOC without first contacting the holder of the utility account (meaning your electric company is going to contact you to see if that is valid before they act on it), so you should consider how you will notify your account holders that are using the old RT# that it is going away and to convert to new RT#.
While you're at it, may as well think about how you will convert those with old checks using old RT# too.
FRB requires you to complete the FRB FedACH Participation Agreement - Part 7, Merger Options, and have it signed and submitted by your institution's EUAC. They will ask that your volume be very small, less than 25 items per month being received on the old RT#.
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