The case for paying extra on a mortgage is arithmetic and it is not in dispute. A dollar of principal removed in month 12 of a 360-month loan avoids interest on that dollar for 348 remaining months. The same dollar in month 300 avoids it for 60.
What goes wrong is not the arithmetic. It is that the money arrives at the servicer with no instructions, and what happens next is their default rather than your intention.
The three defaults
Send $200 beyond your scheduled payment and one of three things happens.
Applied to principal. The balance drops by the extra $200 on top of the scheduled amortisation. Every future month’s interest is calculated on a smaller balance. This is what you wanted.
Held in suspense. The money sits in a holding account until it accumulates into a full scheduled payment, then posts as one. While it waits it reduces nothing and earns you nothing.
Treated as the next payment. The servicer credits it toward next month and advances your due date. Your account shows “paid ahead” or “next payment due” a month later than it was. The balance is essentially unchanged.
Only the first reduces what the loan costs. The third is the one that surprises people, because the account looks healthier while the thing you were paying for has not happened.
What it costs to get this wrong
Take $300,000 at 6.5% over 30 years. The scheduled payment is $1,896.20.
Add $200 a month applied to principal and the loan clears substantially early, with a large interest saving, because each extra dollar removes interest for every remaining month. Our biweekly calculator computes the same mechanism for the twenty-six-payment case.
Add $200 a month that is held in suspense and posted as a scheduled payment and you have simply paid early. The loan matures on the same date. The interest is the same. You have given the servicer the use of your money for nothing.
The difference between those two outcomes is a sentence on a payment instruction.
What to do about it
Say what the money is for, every time. Most servicers offer a “principal only” field in online banking, a separate principal-only payment option, or a box on the coupon. Use it. A memo line on a cheque is weaker than a designated field but better than nothing.
Send it separately from the scheduled payment. A single payment of $2,096.20 is ambiguous. A payment of $1,896.20 and a separate principal-only payment of $200 is not.
Check the balance, not the payment history. The next statement should show the balance lower than scheduled amortisation alone would produce. If the due date moved forward instead, the money went to the wrong place.
If your due date advanced, call and ask for it to be reapplied. Servicers generally will, and the sooner you ask the less interest you have lost.
Where the rules sit
There is less rule here than you might expect. Federal servicing rules govern how a servicer must handle a payment that is a full scheduled payment, and the disclosure framework around your loan sits in Regulation Z, 12 CFR 1026. The Consumer Financial Protection Bureau’s glossary of mortgage terms defines the vocabulary a servicer will use when you ask.
What is not regulated is the default behaviour for money beyond a scheduled payment. That is servicer policy, which is exactly why the instruction has to come from you.
What this site assumes
Our calculators apply an extra payment to principal, in the month it is made. That is the best case, and it is the one the arithmetic of paying extra assumes.
If your servicer is doing something else, the figures here are still correct about what paying extra is worth. They are just describing an outcome you are not getting yet.
Questions
- What happens to extra money if I do not say what it is for?
- It depends entirely on the servicer. Three defaults are common: applying it to principal, holding it in suspense until it adds up to a full payment, or treating it as the next month's payment and marking your account paid ahead. Only the first reduces your interest, and it is not always the default.
- What is "paid ahead" and why is it a problem?
- It means the servicer has credited your extra money toward next month's scheduled payment rather than the balance. Your due date moves forward and your balance barely changes, so you have prepaid a payment instead of removing principal. The interest saving you were paying for does not happen.
- How do I tell whether it worked?
- Check the principal balance on the next statement, not the payment history. If a $200 extra payment reduced the balance by $200 more than the scheduled amortisation would have, it was applied to principal. If the balance moved by the scheduled amount and the due date jumped, it was not.
- Is a suspense account normal?
- It is common and it is not necessarily wrong. A partial payment that cannot be applied as a full scheduled payment often sits in suspense until enough accumulates. The problem is that money in suspense is earning you nothing and reducing nothing while it waits.