If they accept the "shorted" pmt, it will not change anything. They will assess a late fee on 16th of the month, even if it is only short by a dollar. Once it gets to the beginning of the next month, the loan will be 30 days delinquent; it only changes the amount due to bring it current. Remember, all of this is now computerized, and if the computer has that $500 is due on Jan 1 and someone puts into the system an "applied pmt" of $400, it will reduce the amt owed to $100, but it will not change the due date to the next month until the whole pmt is satisfied. Once it hits 90 days past due (if I remember correctly) it is sent for foreclosure. Only after it hits the foreclosure process are they restricted from accepting either the whole amount