Pay Off Mortgage Early Or Invest? Find Your Break-Even Rate

(MENAFN- Thousandaire) > Every extra dollar you send to mortgage principal earns exactly your mortgage rate. Guaranteed, no market risk, no statement to check. So the question isn't“pay it off or invest?” in the abstract. It's whether your rate beats what a safe investment pays after tax, and right now the answer splits sharply depending on when you got your loan.

Prepaying is a bond, not a stock

Treat an extra principal payment as what it is: a risk-free investment that pays your mortgage rate.

That makes the fair comparison a risk-free investment, not the stock market. Comparing a guaranteed 7% to a hoped-for stock return mixes two different bets. Stocks belong in the long-term plan either way. The decision here is narrower: where does your safe money do the most work?

The safe benchmark is short-term Treasury debt. As of October 21, the 1-year Treasury yielded 4.52% and the 10-year 5.13%. Treasury interest also has a quiet perk: only federal tax applies, and it's exempt from state and local income tax.

New borrowers are paying a lot more than that. Freddie Mac's weekly survey put the average 30-year fixed rate at 7.32% for the week of October 22, 2026.

The tax wrinkle that decides it

Treasury interest is taxed. The interest you avoid by prepaying usually isn't a deduction you were getting anyway.

Mortgage interest is only deductible if you itemize on Schedule A. Plenty of households take the standard deduction instead; for reference, the 2026 standard deduction is $16,100 for single filers and $32,200 for joint filers. If you take the standard deduction, your mortgage rate is your after-tax rate. Every dollar of interest you avoid is a full dollar.

So the math compares your full mortgage rate against the Treasury yield minus federal tax.

Two example households

Take two different households, each with $10,000 of spare safe cash. We're using $10,000 because it's round and the percentages carry to any amount.

Household one: single, newer loan. Taxable income lands in the 22% bracket, which for single filers runs from $50,400 to $105,700. The mortgage is from 2025, at 7%.

Put the $10,000 in a 1-year Treasury at 4.52%. That earns $452 in interest. Federal tax at 22% takes $99.44. That leaves $352.56 after tax.

Send the $10,000 to principal instead. At 7%, that avoids $700 of interest in the first year.

$700 minus $352.56 is $347.44. Prepaying wins by almost double.

Household two: married, 2021 loan. Taxable income sits in the 12% bracket, which for joint filers runs up to $100,800. The mortgage rate is 3%.

The same Treasury earns $452. Federal tax at 12% takes $54.24. That leaves $397.76 after tax.

Prepaying at 3% avoids $300 of interest.

$397.76 minus $300 is $97.76. The Treasury wins, and the cash stays reachable.

$10,000 of safe cash	Household one (22%, 7% loan)	Household two (12%, 3% loan)
Treasury interest	$452.00	$452.00
Federal tax on it	$99.44	$54.24
Treasury, after tax	$352.56	$397.76
Interest avoided by prepaying	$700.00	$300.00
Winner	Prepay, by $347.44	Treasury, by $97.76

Same $10,000. Opposite answers.

Find your break-even rate

You don't need either household's numbers. You need one line of arithmetic.

Take the Treasury yield. Multiply it by one minus your federal bracket. That's your break-even mortgage rate. In a spreadsheet: =0.0452*(1-0.22).

At today's 4.52% yield:

12% bracket: 4.52% times 0.88 is about 3.98%. 22% bracket: 4.52% times 0.78 is about 3.53%. 24% bracket: 4.52% times 0.76 is about 3.44%.

If your mortgage rate is above your break-even, prepaying beats the safe alternative. If it's below, park the safe money in Treasuries and let the cheap loan sit there.

A new loan at today's average rate clears every number on that list by more than three points. A 3% loan from a few years back clears none of them.

State income tax tilts things slightly toward Treasuries, since that interest skips state tax. In a high-tax state, nudge your break-even up a little.

If you itemize

Itemizers get to deduct mortgage interest, which lowers the loan's real cost. A 7% loan for someone in the 24% bracket costs 7% times 0.76, or 5.32%, after the deduction.

That's still above the 3.44% break-even for that bracket. A 7% mortgage beats Treasuries even with the deduction. The deduction only flips the answer for rates already near the line.

What about the stock market?

Stocks are a separate decision, and they don't get settled here.

Money you'd invest for twenty years belongs in a diversified index fund whether your mortgage is 3% or 7%, because the expected payoff and the risk are both larger. Draining a retirement plan to kill a mortgage trades a long-run engine for a smaller payment.

The prepay question is about the slice of money you've already decided shouldn't ride the market: the cash beyond your emergency fund, a bonus you won't risk, a house fund you stopped needing. For that slice, the only fair competitor is another safe asset.

Keep the two buckets separate and the decision stops being a philosophy argument.

What prepaying costs you

Liquidity. Money sent to principal is locked inside the house. You can't pull it back out without selling, refinancing, or borrowing against the home, and a lender decides the terms of that last one, not you.

A Treasury matures or sells in days.

That's why prepaying comes after the cushion is built, not instead of it. A 7% guaranteed return isn't worth much if a job loss forces you onto a credit card at a far higher rate.

The move to make

Work out your break-even with the formula above, using the current 1-year Treasury yield and your federal bracket.

If your rate is above it, and you already have an emergency fund, take the full employer match, and carry no high-interest debt: set up a recurring extra principal payment. Tell your servicer to apply it to principal, and check the next statement to confirm it did.

If your rate is below it, leave the mortgage on schedule. Put the spare safe money in Treasuries or a Treasury fund, where it earns more after tax and stays reachable.

This isn't for anyone still building an emergency fund, anyone with credit card balances, or anyone planning to sell within a year or two, where the cash would serve better kept liquid for the move.

Sources Board of Governors of the Federal Reserve System, Selected Interest Rates (Daily), H.15, released October 22, 2026 TreasuryDirect, Interest Income Reporting for Marketable Treasury Securities Freddie Mac, Primary Mortgage Market Survey, Mortgage Rates, week of October 22, 2026 Internal Revenue Service, Publication 936 (2025), Home Mortgage Interest Deduction Internal Revenue Service, Rev. Proc. 2025-32 (2026 inflation adjustments) Thousandaire Editorial Team

The Thousandaire Editorial Team creates practical, evidence-based personal finance content for people building real wealth. We break down investing, retirement, taxes, real estate, and other wealth-building decisions with clear explanations, real numbers, and no hype

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