Prepayment
Adjustable rate mortgages, like other types of mortgage, usually allow the borrower to prepay principal (or capital) early without penalty. Early payments of part of the principal will reduce the total cost of the loan (total interest paid), but will not shorten the amount of time needed to pay off the loan like other loan types. Upon each recasting, the new fully indexed interest rate is applied to the remaining principal to end within the remaining term schedule.
If a mortgage is refinanced, the borrower simultaneously takes out a new mortgage and pays off the old mortgage; the latter counts as a prepayment.
Some ARMs charge prepayment penalties of several thousand dollars if the borrower refinances the loan or pays it off early, especially within the first three or five years of the loan.
Read more about this topic: Variable-rate Mortgage