Pay Off Your Mortgage Early or Invest? How to Decide

Every extra dollar you put toward your mortgage earns a guaranteed, risk-free return equal to your interest rate; investing that dollar instead only comes out ahead if your after-tax investment return beats that rate, and that return is never guaranteed. So the higher your mortgage rate, the stronger the case for prepaying; the lower it is, and the longer you can stay invested, the stronger the case for investing.

Before either, most people should have an emergency fund and no high-interest debt. This guide walks through the comparison, the rules on prepayment penalties, and a worked example you can redo in our calculators.

Do these first

1. 1

   Build an emergency fund

   Money paid into your mortgage is hard to get back: you would have to borrow against the house or sell. The CFPB describes an emergency fund as a cash reserve for unplanned costs like home repairs, medical bills or lost income, kept somewhere safe and accessible. Size yours with our homeowner emergency fund calculator.
2. 2

   Pay off high-interest debt

   A credit card at 20%+ is a far better “investment” to pay off than a mortgage at 6%.
3. 3

   Capture any employer retirement match

   A match is an immediate return that prepaying can’t equal.
4. 4

   Then compare prepaying with investing

   Use the framework below.

The comparison, side by side

What your “guaranteed return” really is

If your rate is 6.5%, each dollar of extra principal saves 6.5% a year in interest for as long as the loan would have run. Taxes can shrink that a little: if you itemize and deduct mortgage interest, part of the interest you save was tax-deductible, so your after-tax return from prepaying is lower. Under IRS Publication 936, you can deduct home mortgage interest only if you itemize on Schedule A, and for loans taken out after December 15, 2017, only interest on up to $750,000 of acquisition debt ($375,000 if married filing separately) counts. If you take the standard deduction, your after-tax return from prepaying is simply your rate. See who still benefits from the deduction.

Investment returns work the other way: they are uncertain, and gains may be taxed unless they are in a retirement account. To compare fairly, use the return you expect after taxes and fees, and remember that a few bad years can land right when you need the money.

Worked example: $500 a month, two ways

Take a $500,000, 30-year fixed loan at 6.5%. The principal-and-interest payment is $3,160.34, and over 30 years you would pay $637,722 in interest. Now suppose you have an extra $500 a month.

Prepaying $500 a month for 20 years (about $120,000 of extra payments) cuts the balance $245,210 below where it would have been. Investing the same $500 a month instead would grow to:

The math confirms the rule: if your after-tax return equals your mortgage rate, it is a tie. Prepaying wins at lower returns and investing wins at higher ones. The difference is that the prepaying column is certain and the investing column is not, while the investing column is money you can reach and the prepaying column is not.

How prepaying actually works

• Mark it as principal. Most servicers let you add an amount labeled “additional principal” online or on the coupon. Check your next statement to confirm it reduced the principal, not escrow or a future payment.
• Your required payment doesn’t drop. On a fixed-rate loan, extra principal shortens the term; the monthly payment stays the same. If you want a lower payment instead, ask about a recast.
• Watch how partial amounts are handled. Under Regulation Z, a servicer must credit a full periodic payment on the day it arrives, but it may hold a payment smaller than a full installment in a suspense account until enough builds up. Sending “extra” as a separate principal payment avoids confusion.
• Lump sums vs. monthly extras. Both work. Earlier dollars save more because they stop interest sooner.

Prepayment penalties

The CFPB notes that penalties typically apply when you pay off the whole loan early (by selling or refinancing), sometimes when you pay off a large amount at once, and do not normally apply to small extra principal payments. Your note and closing documents say whether your loan has one; ask the servicer if unsure.

When prepaying tends to make more sense

• Your mortgage rate is high relative to safe returns you could earn elsewhere.
• You already have a full emergency fund and are on track with retirement savings.
• You plan to stay in the home and want to retire without a mortgage payment.
• Market risk would keep you up at night, or you would likely sell investments in a downturn.

When investing tends to make more sense

• Your rate is low, for example a loan locked in when rates were near historic lows.
• You have a long time horizon and can ride out market drops.
• You lack liquid savings, or you have tax-advantaged retirement room left to fill.
• You may move or refinance soon, which limits how long a prepayment pays off.

General information, not financial advice. Investment returns are not guaranteed; consider a fee-only adviser for your full picture.