A 58-Year-Old Orthodontist Discovers How to Shield $300,000 From Taxes Using a Hidden 401(k) Strategy

A 58-year-old orthodontist pulling roughly $700,000 in annual profit from a three-employee practice has already maxed out a 401(k) and watches another $200,000 land in the top federal bracket. The standard playbook runs out at the $72,000 combined employee-plus-employer ceiling for 2026, leaving a six-figure tax bill that feels inevitable but is not.

A cash balance plan layered on top of the 401(k) can absorb another $150,000 to $250,000 in pre-tax dollars every year. For an owner in the late 50s or early 60s, this structure is routinely dismissed as too complicated, or simply overlooked. That is a costly mistake. The IRS treats cash balance plans as defined benefit plans, and the funding limit grows larger the fewer working years remain before retirement.

Why the Limit Explodes After 50

A cash balance plan is a defined benefit plan built to function like a 401(k). Each participant holds a hypothetical account that grows through a pay credit fixed in the plan document, plus an interest credit often tied to the 10-year Treasury yield. That benchmark was running near 4.7% in mid-August 2026, up from around 4.6% in late July and continuing a climb driven by rising federal debt issuance and persistent inflation concerns. The IRS caps the maximum annual benefit a participant can receive at $290,000 for 2026 under Section 415(b). To fund that promised benefit across a shrinking number of working years, an actuary works backward to a deductible contribution that grows the closer the owner is to retirement.

The age-based math is striking. For a 55-year-old, the calculation typically supports a deductible contribution near $200,000. By age 60, it climbs above $260,000. By 65, it can exceed $300,000. An enrolled actuary certifies this figure annually, drawing on the owner’s compensation, age, and the plan’s interest crediting assumption. The IRS compensation limit for these calculations is $360,000 for 2026, and the lifetime lump-sum accumulation cap sits at approximately $3.7 million.

The rising yield environment carries a planning nuance worth knowing. Cash balance plans that use a Treasury-linked interest crediting rate can see their actuarially permitted contributions shift as yields move. With the 10-year now pushing toward the 4.7% range and some market observers expecting it to cross 5% before year-end, plan sponsors should confirm with their actuary that contribution projections remain current. Generally speaking, higher crediting rates compress the contributions needed to fund a given future benefit, while lower rates have the opposite effect.

Stacking the Two Plans

The cash balance plan sits on top of the 401(k). A typical stack for a 58-year-old owner looks like this:

1. 401(k) employee deferral. The 2026 base limit is $24,500, plus the age-50 catch-up of $8,000, for $32,500 total. Owners who earned more than $150,000 in 2025 FICA wages must route that catch-up to a Roth 401(k) under the SECURE 2.0 rule, which took effect January 1, 2026. The IRS issued final regulations with a good-faith compliance standard available through 2026, so the upfront pre-tax deduction shrinks to $24,500 for high earners directing their catch-up dollars to Roth. One additional note for this owner: at age 60, SECURE 2.0’s “super catch-up” provision kicks in, raising the catch-up ceiling to $11,250 in place of the standard $8,000.
2. Profit sharing contribution. The employer side fills the remainder of the $72,000 combined ceiling, typically around $46,500 for an owner taking the full salary deferral. This contribution is fully deductible to the business. When pairing a cash balance plan with a 401(k), the IRS generally limits profit sharing to 6% of covered compensation rather than the full ceiling.
3. Cash balance contribution. A separately deductible defined benefit contribution, sized by the actuary. For a 58-year-old earning $345,000 or more in W-2 wages, a contribution of $200,000 is realistic.

Add the three buckets and the owner has shielded close to $300,000 from current taxes. At a 37% federal marginal rate plus state, the first-year cash savings can approach $120,000.

The Catches Worth Knowing

Employees must be covered too. A cash balance plan has to satisfy IRS nondiscrimination testing, which typically requires the employer to contribute 5% to 8% of pay for staff. For a practice with three employees each earning $60,000, that cost runs roughly $12,000 a year. The owner’s tax savings still far exceed the employee expense, but the plan only makes sense when an older, higher-paid owner works alongside a younger, lower-paid workforce.

The plan also demands commitment. The IRS expects contributions for at least three to five years. Skipping a year without formally amending the plan triggers excise taxes. The current Treasury yield environment matters here because the interest crediting assumption shapes how much can be contributed each year. With yields now near 4.7% and rising, plan sponsors who set projections earlier in the year may find their actuary needs to revise contribution estimates before year-end funding deadlines arrive.

What to Do Before Year-End

1. Run a feasibility study. A third-party actuary will model your exact deductible contribution based on W-2 income, age, and employee census. Most firms provide this analysis at no cost as part of winning the design work.
2. Adopt the plan by December 31. A cash balance plan must be in place by the last day of the fiscal year to generate a deduction for that year. The funding itself can wait until the tax filing deadline, including extensions.
3. Coordinate the 401(k) restatement. Pairing the two plans requires amending the 401(k) to a safe harbor design and realigning employee contributions to satisfy combined nondiscrimination testing. Skipping this step is the most common reason cash balance plans fail an audit.

For an owner staring at a $200,000 tax bill on the last slice of profit, this is the single largest legal deduction the tax code still offers high earners. The window to use it for 2026 closes December 31.

Editor’s note: This article was updated to reflect the 10-year Treasury yield rising to approximately 4.7% as of mid-August 2026, the potential implication of yields approaching 5% for cash balance plan actuarial assumptions, and the SECURE 2.0 super catch-up limit of $11,250 available to plan participants ages 60 to 63 starting in the year they turn 60.

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