When it comes to mortgage advice, some people recommend making an extra payment. The logic is :"These extra payments are automatically applied to your principal, not interest".

Why does it matter if the extra payment is applied to the principal and not interest?

  • If you pay an an additional amount over your payment and it is designated to go to the principal, do they legally charge interest on the additional amount?
    – Tom Daniel
    Commented Aug 7, 2017 at 21:18

6 Answers 6


Applying to principal now reduces the interest through the life of the mortgage. If you have principal of 100K and 10% APY, then by the end of the year (assuming no other payments are made) you'll owe 110K.

If you have a spare 1K and apply it to interest by the end of the year you'll owe 109K, but by the end of the next year you'll owe 119.9K.

If you apply it to principal, by the end of the year you'll owe 108.9K, and by the end of the next year you'll owe 119.79K.

Overall, just by applying to principal and not making any other payment, you saved 100 additional dollars in one year. Now, think of a 30-years fixed rate mortgage.


Extra payments apply towards principal, and since interest is amortized and computed monthly.

The impact on your loan is pretty amazing. One extra payment per year will take about 8 years off of a 30 year fixed mortgage.

See a tool like http://www.mortgagecalculator.org for examples.


I'm not sure where the "not interest" part of your quoted statement comes from; that's not the way this advice is normally given. Perhaps you worded the statement that way because you think there are only two possibilities: payments either are applied to the principal or to the interest? If so, there's a misunderstanding here.

Here are two other possibilities: (1) the mortgage holder puts the extra payments in escrow/holding, to be used in the future should you fail to make a payment; (2) the mortgage holder records the payment as being made in advance, without giving you any benefit (such as reduced interest). (Another way of thinking of this is that the mortgage holder moves up the due date, essentially giving you credit for having made the final payment. Unfortunately, this isn't just theoretical.)

In short, "applied to principal" is a shorthand way of saying that the mortgage holder treats the extra payment in a particular way (which benefits you the most), and not in a way (see (1) and (2), above) that benefits the mortgage holder the most.

  • It's exactly the way I've always heard this advice given - because interest is amortized and calculated monthly, paying more now means you shorten the life of the loan. See @littleadv's answer
    – warren
    Commented Apr 25, 2011 at 14:05
  • In other words, if you make a double-payment in August, you want the extra to be used to immediately reduce the principal, not treated as an advance payment of September's normal payment. The latter option benefits the lender, so unless laws or your instructions specify otherwise, this might be what they'll do.
    – TripeHound
    Commented Aug 8, 2017 at 15:16

This can be misleading.

Earlier payments are not automatically applied to principal in many jurisdictions. They are instead immediately applied to payments. In other words, over the life of a mortgage, many payments are scheduled, and they can even vary if the mortgage is not fixed-rate. If early payments are sent without specification in some jurisdictions, principal & interest may not even be prepaid instead payments will be accrued, so the principal is not reduced, thus interest is still being accrued off of the unreduced principal, and the investors or processor receives an interest-free short term loan in the form of a "payments accrued" account. This serves to raise the interest rate for the borrower and lower it for the lender or processor. As payments are due, and no new payments are made, the payments accrued account funds the payment due.

Early payments must be specified to "apply to principal". They could even be applied to interest, but this would be a waste since it effectively raises the interest rate.

Paying the principal instead of a full payment or even interest alone will reduce the amount owed, substituting cash for equity assuming the value of the home doesn't fall, while keeping the interest rate constant. Paying any payment or interest early only serves to increase the investor's interest rate since that money is received faster and can be reinvested elsewhere.

  • Thanks. Can you elaborate:"They are instead immediately applied to payments."
    – Victor123
    Commented Jan 30, 2014 at 14:40

Let's say you are paying $500 a month, and this month you pay $1,000 extra, for a total of $1,500. "Counts towards principal" means you now owe the bank $1,000 less. You still have to make your $500 payments this month and next month, but your loan will be repaid a lot quicker. Every month you pay less interest, because you owe less money, so more of each months payment goes towards paying back the loan.

"Counts towards interest" means your payments are now $1,000 ahead of schedule, so you could not pay any money in the next two months (because you already made these two payments). So you haven't really paid back any additional money, but the bank holds these $1,000 for you and uses the money if you don't make payments. So this is much less beneficial to you.


Assume the following mortgage. (see table below)

The interest amount in any given month is OPENING_BALANCE * ANNUAL_RATE / 12 (months per year).

So in the first month, the charge to borrow the money for 1 month is $1,250. We pay the bank $2,000. They take the $1,250 off the top, and apply the remainder to our principal.

Now look at month two. Our principal has been reduced by $750, Our interest is reduced by $4, and our payment stays the same. This means that an extra $4 off of principal compared to the previous month.

Now look at month 12. For that month, I've applied an extra payment of $10,000 on top of my regular payment of $2,000. Notice that the interest due that month is $1,204, The bank will skim their charge off the top of my payment, leaving $10,796 to be applied to principal.

As Sharptooth said HERE, the monthly interest is the amount we pay to keep them from demanding repayment of the entire loan right now. Everything else we pay goes to reduce our principle balance.

As for making an extra payment of $2000, the easiest way to do this is to switch your payments to bi-weekly. Instead of paying $2,000 a month ($24,000), you'll pay $1,000 every two weeks. Since there are 52 weeks in a year, you'll end up making 26 payments, for a total of $26,000. This works really well if you are paid bi-weekly, since the months with the extra payments end up being the months with the extra paycheques. On a 25 year mortgage, this plan will have you debt free nearly 6 years earlier. If you are paid monthly, then you're best alternative is to simply increase your monthly payment to 13/12 of what it currently is.

Principle   Rate    Period  Payment
$250,000     6%      25       $2,000 

Date    Open           Interest Payment          Extra      Close
01-Jan-14   $250,000    $1,250  ($2,000)     $-             $249,250 
01-Feb-14   $249,250    $1,246  ($2,000)     $-             $248,496 
01-Mar-14   $248,496    $1,242  ($2,000)     $-             $247,739 
01-Apr-14   $247,739    $1,239  ($2,000)     $-             $246,977 
01-May-14   $246,977    $1,235  ($2,000)     $-             $246,212 
01-Jun-14   $246,212    $1,231  ($2,000)     $-             $245,443 
01-Jul-14   $245,443    $1,227  ($2,000)     $-             $244,671 
01-Aug-14   $244,671    $1,223  ($2,000)     $-             $243,894 
01-Sep-14   $243,894    $1,219  ($2,000)     $-             $243,113 
01-Oct-14   $243,113    $1,216  ($2,000)     $-             $242,329 
01-Nov-14   $242,329    $1,212  ($2,000)     $-             $241,541 
01-Dec-14   $241,541    $1,208  ($2,000)     $-             $240,748 
01-Jan-15   $240,748    $1,204  ($2,000)     $(10,000.00)  $229,952 
01-Feb-15   $229,952    $1,150  ($2,000)     $-             $229,102 
01-Mar-15   $229,102    $1,146  ($2,000)     $-             $228,247 
01-Apr-15   $228,247    $1,141  ($2,000)     $-             $227,389 

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