The Four Options

Option 1: Pay it off now from savings. Eliminate the mortgage today. Bank what would have been the monthly payment for the remaining years of work. Reduces required retirement withdrawals by the mortgage payment forever.

Option 2: Wait until retirement (e.g., 2 years). Continue paying through the working years; pay off the smaller balance at retirement. The principal drops by ~$30K of normal amortization. Leaves the savings invested for two more years at market returns.

Option 3: Carry it into retirement and pay from the 401(k). Keep the mortgage. Continue paying it after retirement, with each payment ultimately funded by IRA/401(k) withdrawals. Preserves market exposure on every dollar that would have gone toward early payoff.

Option 4: Other. Refinance to a lower rate (if possible), recast the loan with a partial principal payment to reduce monthly payment, or set up a HELOC as a liquidity backstop to enable a more aggressive payoff.

The Variable That Decides It: Where the Payoff Money Comes From

A $125,000 payoff funded from each of three sources has very different tax implications:

• From a savings or money-market account: Roughly zero tax cost. Just opportunity cost — what that $125K would have earned at perhaps 4–5% in cash or 5–7% in equity.
• From a taxable brokerage account: Capital gains tax on the realized portion only. For a position with $30K of long-term gains, taxes might run $4,500 federal plus state. Real, but bounded.
• From a pre-tax 401(k) or IRA: Every dollar withdrawn is ordinary income. To net $125K after federal + state tax in the 24% bracket, the gross withdrawal is roughly $165K–$170K. The hidden tax cost: $40K–$45K. Plus the withdrawal can stack into IRMAA tiers, ACA subsidy losses, or bracket creep.
• From a Roth: Tax-free, but you give up the most valuable retirement dollars in your portfolio.

The same $125K mortgage costs a wildly different amount to retire depending on which account you tap. The decision rarely comes down to “mortgage rate vs. expected return.” It comes down to “effective cost of payoff vs. value of debt elimination.”

Real Scenario: $125K at 4.78%, Two Years Out

A pre-retiree 2 years from retirement with a 4.78%, $125K mortgage maturing in 2033 (8 years left), a 401(k) of $1.2M, a $300K taxable brokerage, $50K cash, and a small pension.

Path A — Pay off now from taxable. Sell $130K from the brokerage, pay roughly $5K of long-term capital gains tax, retire the mortgage. Bank the freed-up monthly payment (~$1,575) for the remaining work years (~$38K total). Enter retirement with no mortgage and a $300K taxable buffer reduced to ~$200K (after gain). Required retirement withdrawal is lower for the rest of life.

Path B — Wait 2 years, then pay off from taxable. Continue paying for 2 years. Principal drops to ~$95K. Brokerage compounds for 2 years (worth ~$330K with average returns). At retirement, pay off $95K from the brokerage. Tax cost on $95K sale ~$3,500. Slightly larger residual taxable balance compared to Path A. Outcome is essentially equivalent — small advantage to Path B if markets cooperate during the bridge, small disadvantage if they don't. This is a marginal optimization, not a strategic choice.

Path C — Carry into retirement, pay from the 401(k) monthly. Each $1,575 mortgage payment in retirement requires roughly $2,070 of 401(k) withdrawal at the 24% bracket. That's $24,840/year of additional gross IRA withdrawal vs. a mortgage-free retirement. Over 6 remaining years of mortgage payments, that's ~$149,000 of additional IRA withdrawal, which can stack into IRMAA tiers and reduce ACA subsidies in the pre-65 years. The 4.78% mortgage rate looks reasonable on paper — but the after-tax cost of servicing it from a pre-tax account is closer to 6.3%. That's harder to beat with conservative portfolio returns.

The verdict: Path A or B is usually the right call. Path C is the worst path because of the compounding tax drag. The question of paying off now vs. waiting two years is a minor optimization. The question of paying off from taxable vs. pre-tax is the real decision.

When Carrying the Mortgage Wins

Despite the math above, there are situations where carrying the mortgage into retirement is structurally correct:

• The mortgage rate is well below current after-tax fixed income returns. A 2.5% mortgage paid off with 5% cash equivalents is giving up real money.
• The household has no taxable buffer. Pulling the entire payoff from a 401(k) destroys liquidity and forces a large bracket year.
• The mortgage payoff would consume the cash reserve needed for the first 2-3 years of retirement. Liquidity for sequence-of-returns risk often outranks debt elimination.
• The household values keeping the option open. Mortgage debt is structurally optional — you can always pay it off later — while a 401(k) withdrawal is irreversible.

The Behavioral Side

The math gets you part of the way to the answer. The other part is what eliminating debt does to the rest of the plan.

A retiree without a mortgage withdraws less from the portfolio, which means lower required AGI, lower IRMAA exposure, lower sequence-risk vulnerability, more flexibility to flex spending down in a bad market year. None of those benefits show up in a simple mortgage-rate-vs-return comparison.

A retiree without a mortgage also sleeps differently. That's not a financial argument. It is, for many households, a real input. The right answer balances both sides.

Common Mistakes

• Pulling $125K+ from a pre-tax 401(k) in a single year to pay off a mortgage and triggering a 24%+ federal bracket plus IRMAA.
• Comparing mortgage rate to expected market return without adjusting for tax cost of the payoff source.
• Eliminating the cash reserve to pay the mortgage and entering retirement with no liquidity buffer.
• Ignoring the value of a smaller required retirement withdrawal for the rest of life.
• Treating “wait two years” vs. “pay now” as a strategic choice when it is a marginal optimization.

The Bottom Line

The mortgage-payoff decision is rarely about the rate alone. It's about the source of the payoff dollars, the size of the required retirement withdrawal that gets eliminated, the household's liquidity buffer, and the peace-of-mind value of a house with no debt against it.

For most households at moderate rates, paying off from taxable savings — now or in the early retirement window — beats carrying the mortgage and servicing it from a pre-tax account. Whether you do it the day before retirement or a year before is a marginal optimization, not the actual decision.