Prenote ACH Entries are $0 transactions sent to verify an ACH Receiver’s routing number, account number & account type at another institution. This helps ensure the entries are sent to an open & active account. While prenotes are recommended, they are not required. Prenotes must be sent a minimum of three business days before the first “live” transaction processes to the account. This provides time for the receiving institution to return or send a correction notice if any account data needs to be updated.