A prenote is the commonly used term for an Automated Clearing House (ACH) prenotification.
Prenotes are optional for the originating company, but they are not optional for the receiving bank or credit union (the RDFI, or receiving depository financial institution) once the originating company sends one. Under the ACH rules’ National System of Fines, an RDFI can be fined if they do not validate prenotes sent to them.
Under NACHA Operating Rules (also known as ACH rules), a prenote’s purpose is to “validate” the routing number and account number of the receiving bank or credit union.