"... no later than the opening of business on the banking day following the sixtieth calendar day following the settlement date of the original entry"

"... no later than the opening of business on the banking day following the sixtieth calendar day following the settlement date of the original entry" From my notes, quoted from the NACHA spec a few years back. So, settlement date is the next day (mostly). + 60 days, then the next morning that banks are open. So, if 60 days is Thursday, Christmas Eve, then the next Monday morning is the cutoff.