The 13th Payment Strategy: How One Extra Mortgage Payment a Year Slashes Your Interest

If you're searching for a low-risk way to own your home free and clear sooner, paying one extra mortgage a year is one of the most effective habits a homeowner can build. This single additional payment, made once annually, goes straight toward your principal balance and compounds into real interest savings over the life of the loan. Run the numbers through a mortgage calculator with extra payments and the impact becomes obvious — often several years shaved off a 30-year term and tens of thousands of dollars kept out of your lender's pocket.

Does Making One Extra Mortgage Payment a Year Actually Help?

Yes — and the effect is larger than most homeowners expect. A standard 30-year mortgage is structured so that early payments are weighted heavily toward interest rather than principal. Every dollar you add on top of your regular payment skips that structure entirely and applies directly to the balance, which means your lender calculates next month's interest on a smaller number. That small shift, repeated every year for the life of the loan, is what makes paying one extra mortgage a year such an efficient strategy compared to simply saving the same money elsewhere at a lower return.

Consider a $320,000 loan at 6% over 30 years — the same example used throughout LoanRateCheck's own tools. The standard monthly principal-and-interest payment is roughly $1,919. Committing to one extra payment of that size each year, whether as a lump sum or spread across twelve months, can cut the loan term by four to six years and reduce total interest paid by $50,000 or more, depending on when in the loan you start. Homeowners who begin the habit in year one or two see the largest gains, since that's when the biggest share of each payment is still going to interest.

The Math Behind a Single Annual Extra Payment

The mechanics are straightforward: interest accrues monthly on your outstanding balance, so any reduction to that balance lowers every future interest calculation, not just the next one. An extra payment calculator makes this visible instantly — enter your loan amount, rate, and term, add a single annual extra payment, and compare the new amortization schedule against your original one side by side. The gap between the two payoff dates is the strategy's entire value proposition, expressed in years and dollars rather than abstract percentages.

What makes this approach appealing is that it requires no new loan, no closing costs, and no change to your credit terms. You're not refinancing or renegotiating anything — you're simply redirecting one payment's worth of cash toward the balance each year. For homeowners who received a raise, a bonus, or a tax refund, that source of funds is often already sitting in a checking account waiting for a purpose.

Before committing to a specific dollar amount, it helps to see your current loan's actual numbers rather than a generic example. Plug your balance, rate, and remaining term into LoanRateCheck's extra payment calculator and test a few scenarios — a small monthly addition, a single annual lump sum, and a larger one-time contribution — so you can see which approach fits your budget while still delivering a meaningful reduction in both interest and loan term.

How the Strategy Works: The 13th Payment, Interest Reduction, and Time Saved

The "13th Payment" Concept

Mortgage professionals often call this the "13th payment" strategy because it turns twelve scheduled payments into the financial equivalent of thirteen within a calendar year. That one extra payment doesn't reset your due date or change your required monthly amount — it simply reduces the principal balance the lender uses to calculate interest going forward, which is exactly why the timing and consistency of the habit matter more than the payment method you choose.

Interest Reduction Over Time

Because mortgage interest compounds on a declining balance, an extra payment made early in the loan does more work than the identical payment made in year 25. On our $320,000 example loan, a single extra payment applied in year one can eliminate several hundred dollars of future interest that would otherwise have accrued on that portion of the balance for the remaining term. Multiply that effect across 30 annual extra payments and the total interest savings compound into a genuinely meaningful figure — commonly in the $50,000–$100,000 range on a mid-sized loan at today's rates.

Time Saved on Your Loan Term

The flip side of interest reduction is time. Because your monthly payment stays fixed while the balance shrinks faster, fewer total payments are needed to reach zero. Most homeowners who commit to one extra payment a year finish their mortgage four to six years ahead of schedule, turning a 30-year commitment into something closer to 24 or 25 years without ever increasing their required monthly outlay.

Methods to Execute the Strategy

Lump-Sum Annual Payment

The most direct method is saving throughout the year and submitting one full extra payment — matching your regular principal-and-interest amount — whenever convenient, such as after receiving a bonus or tax refund. This requires discipline to set the funds aside but involves no changes to your automatic payment schedule.

Monthly Division: 1/12 Extra Each Month

Instead of one large payment, divide your regular payment by twelve and add that fraction to every monthly payment. On a $1,919 payment, that's about $160 extra per month. By December, you've contributed the full 13th payment without ever feeling a single large withdrawal from your account.

Bi-Weekly Payment Plan

Switching from monthly to bi-weekly payments — half your normal payment every two weeks — results in 26 half-payments annually, which equals 13 full monthly payments instead of 12. This method works well for borrowers paid bi-weekly themselves, since the payment rhythm matches their paycheck schedule. Confirm with your servicer that bi-weekly payments are accepted and applied without an added processing fee before switching.

Key Considerations Before You Commit

How Principal Application Works

The single most important step in this entire strategy is confirming, in writing, that your extra payment is applied directly to principal rather than sitting as a prepaid credit toward next month's bill. Many servicers require a specific instruction — sometimes a checkbox on the payment portal, sometimes a note in the memo line — to route the funds correctly. Skipping this step is the most common reason homeowners believe the strategy "didn't work" when in fact their extra payments were never actually reducing the balance.

Watch for Prepayment Penalties

Most conventional mortgages originated in recent years carry no prepayment penalty, but it's worth verifying in your loan documents or by asking your servicer directly, especially for older loans or certain non-conventional products. The Consumer Financial Protection Bureau maintains consumer guidance on prepayment terms and is a reliable place to confirm your rights before committing extra funds.

Weighing the Opportunity Cost

Extra mortgage payments are not automatically the best use of spare cash. If your mortgage rate is below what you could reasonably earn investing the same money, or if you're carrying higher-interest debt like credit cards, those obligations typically deserve priority. The strategy makes the most sense once you have an emergency fund in place, no higher-interest debt outstanding, and a mortgage rate that makes guaranteed debt reduction competitive with market returns.

What Is the Best Strategy for Making Extra Mortgage Payments Each Year?

There isn't a single universally "best" method — the right choice depends on your cash flow and discipline. Homeowners with irregular income (commissions, bonuses, self-employment) often prefer the lump-sum approach, saving opportunistically and paying once a year. Salaried homeowners who want a "set it and forget it" system tend to favor the monthly-division method, since it's automated and painless in $100–$200 increments. Before choosing, run each scenario through a mortgage early repayment calculator using your actual loan balance, rate, and term — the numeric difference between methods is usually small, so pick whichever one you'll actually stick with for the full loan term.

Is It Better to Pay Extra on a Mortgage, Monthly or Yearly?

Mathematically, extra payments made monthly save marginally more interest than the same total amount paid once a year, because the balance is reduced sooner and interest has less time to accrue on it. The difference, however, is typically modest — often a few hundred dollars over the life of the loan, not thousands. The larger factor by far is simply whether the extra payment happens consistently every year. A homeowner who reliably makes one lump-sum payment annually will outperform one who intends to pay monthly but stops after a few months. Consistency, not timing, is what determines your actual savings.

Model your own numbers with LoanRateCheck's mortgage calculator with extra payments to see exactly how a monthly versus annual approach plays out on your specific loan balance, rate, and remaining term.