Cash Balance + Solo 401(k) at $300K: Shelter $200K+

Dr. Elena Vasquez is a 52-year-old independent dermatology consultant in Austin, Texas. She files single, runs her practice as a sole proprietorship reporting on Schedule C, and nets $300,000 after expenses. She already maxes her Solo 401(k) at her age-50+ ceiling of $80,000 — the $24,500 employee deferral plus the $8,000 age-50 catch-up plus employer profit-sharing, all inside the $72,000 base limit under IRC §415(c) before the catch-up. She is still writing a large check to the IRS every April and wants to know what comes next.

The answer is a cash balance plan stacked on top of the Solo 401(k). An actuary running her numbers at age 52 will size a year-one cash balance contribution near $150,000. Add that to her Solo 401(k) contribution — trimmed to about $48,000 once the §404 combined-deduction limit caps the employer profit-sharing at 6% of compensation — and Elena deducts roughly $198,000 pretax in a single year, sheltering close to two-thirds of her net income. At her 35% federal marginal rate, the cash balance piece alone defers about $52,500 in federal income tax. Texas has no state income tax, so that is the whole bill.

Why the Solo 401(k) hits a wall at $72,000

The Solo 401(k) is a defined-contribution plan. Its 2026 ceiling is fixed by statute: $24,500 of employee deferral (IRC §402(g)), plus a $8,000 catch-up at age 50+, plus employer profit-sharing — but the combined employee-plus-employer total cannot exceed $72,000 under IRC §415(c), or $80,000 once you add the age-50 catch-up. Elena, at 52, is at her $80,000 wall, and the defined-contribution world is closed. A SEP-IRA would not help — it caps at 25% of compensation up to $73,500, essentially the same ceiling with no catch-up at all.

The only way past $72,000 is a different category of plan entirely: a defined-benefit pension. A cash balance plan is the modern, hybrid version of that pension — and its contribution limit is not a flat number. It is whatever an enrolled actuary certifies is needed to fund your promised benefit.

What a cash balance plan actually is

A cash balance plan is a defined-benefit plan governed by IRC §412 (minimum funding standards) and §415(b) (maximum benefit limits). Instead of promising “X dollars per month at retirement” like a traditional pension, it expresses your benefit as a hypothetical account balance that grows two ways each year:

• A pay credit — the contribution the plan document promises to add, often defined as a flat dollar amount or a percentage of compensation. This is what gets sized to your age.
• An interest credit — a guaranteed crediting rate (commonly 4–5% or pegged to the 30-year Treasury) that the plan promises the balance will earn, regardless of actual investment results.

Because the plan promises a future lump sum, the deductible contribution is reverse-engineered: the actuary calculates how much must go in this year so the account reaches the §415(b) maximum benefit (a lifetime annuity worth up to roughly $3.5 million in lump-sum terms) by your assumed retirement age. The fewer years you have left, the larger the required annual contribution. That is why age is the single biggest lever.

The age lever: why 52 is a sweet spot

Younger high earners can deduct meaningful amounts, but the deduction compounds with age because the funding window shrinks. The figures below are typical actuarial ranges for a solo earner with enough income to support the contribution; your exact number depends on the plan’s benefit formula and interest-crediting rate.

*$72,000 base + $8,000 age-50 catch-up. **Age 60–63 super catch-up is $11,250 instead of $8,000 under SECURE 2.0 §109, so $72,000 + $11,250 = $83,250. The “+ Solo 401(k)” column shows the standalone DC ceiling; once the cash balance plan is in place the §404(a)(7) combined-deduction limit caps the 401(k) employer profit-sharing at 6% of compensation, so the realized 401(k) piece is smaller (roughly $48,000–$56,000 for Elena) — see the worked numbers below. When a defined-benefit plan exists, the Solo 401(k) employer profit-sharing piece is limited to 6% of compensation to stay under the combined-deduction limit, so the employee deferral plus catch-up does most of the work on the 401(k) side.

Elena’s worked numbers

Elena nets $300,000. Her actuary designs a cash balance benefit formula that produces a $150,000 pay credit at age 52. Here is the year-one stack and the tax it shelters.

For 2026, single taxable income from $250,526 to $626,350 sits in the 35% bracket and the band just below ($197,301–$250,525) is the 32% bracket. Elena’s deduction peels dollars off the top of her income, so the tax saved comes off the 35% layer first. A roughly $198,000–$222,000 deduction defers on the order of $70,000 in federal tax in year one — against a $2,000–$4,000 administration cost. The plan pays for itself many times over on the first contribution.

The funding obligation: the reason this is a commitment, not a toggle

A Solo 401(k) is discretionary — contribute $0 in a bad year, no penalty. A cash balance plan is the opposite. It is a pension subject to the minimum funding standards of IRC §412. Once the actuary certifies the required contribution, you must fund it. Miss it and you owe a 10% excise tax on the funding shortfall under IRC §4971, escalating to 100% if the deficiency is not corrected.

1. You commit to fund for multiple years. The IRS expects a qualified plan to be “permanent.” Terminating a cash balance plan in fewer than three years invites the argument that it was never a bona fide retirement plan, which can disqualify the deductions retroactively. Plan to keep it open at least three to five years.
2. The contribution flexes within a range. A well-designed plan builds in a corridor (a minimum and a maximum required contribution) so a soft year does not force a single rigid number. But the floor is still a real obligation.
3. An enrolled actuary must certify funding annually. Each year the actuary signs Schedule SB and the plan files Form 5500 (or 5500-EZ for a true one-participant plan). This is the ongoing administration the $2,000–$4,000 fee covers.

The decision rule is simple: adopt a cash balance plan only if your income is reliably high enough to fund it for at least three to five years. Elena, with a decade-long consulting practice netting $250,000–$350,000 every year, clears that bar. A founder whose income swings from $400,000 to $40,000 should not — the funding floor will become a liability in the lean year.

What most people miss: the 6% profit-sharing haircut and the §404 ceiling

The most common mistake is assuming you keep the full $72,000 Solo 401(k) and the full cash balance contribution. You do not — when a defined-contribution and a defined-benefit plan cover the same person, IRC §404(a)(7) imposes a combined-deduction limit. In practice the actuary preserves your entire $24,500 employee deferral and $8,000 catch-up (those are always yours) but caps the employer profit-sharing piece of the 401(k) at 6% of compensation. You give up some of the profit-sharing match to make room for the far larger cash balance deduction. The net is still hugely positive — trading roughly $20,000 of 401(k) match for a $150,000 cash balance deduction — but the headline “$72,000 plus $150,000” overstates it slightly. The real total for Elena lands near $200,000–$222,000, not $222,000 plus an untouched $72,000.

The second thing people miss: the cash balance assets must be invested conservatively. Because the plan guarantees an interest credit (say 5%), large investment gains create an overfunding problem and losses create an underfunding gap you must make up. The portfolio is built to track the crediting rate — bonds and stable assets, not a growth-stock sleeve. The tax deduction, not market upside, is the product.

When the answer is “not yet”

A cash balance plan is the right move only after three conditions are met. If any one fails, stay with the Solo 401(k) for now.

• You have already maxed the $72,000 Solo 401(k) and still have profit you want to shelter. If you are not maxing the cheaper, more flexible plan first, there is no reason to add a pension.
• Your income is stable and high. The rule of thumb among pension administrators is roughly $250,000+ of reliable net income to justify a six-figure contribution. Lumpy income breaks the funding math.
• You are 45 or older. Under 45, the actuarial contribution is smaller and the multi-year commitment is harder to justify against the administration cost. The strategy gets dramatically more powerful at 50, 55, and 60.

The exit: rolling the balance to an IRA

When you eventually wind the plan down — at retirement, on a practice sale, or after the funding window closes — you roll the accumulated cash balance into a traditional IRA tax-free, where it continues to grow tax-deferred until RMDs begin (age 75 if you were born in 1960 or later, under SECURE 2.0 §107). The deduction was taken at your peak 35% rate; the distributions later may land in a lower bracket. That rate arbitrage, on top of years of tax-deferred compounding, is the back half of the strategy.

The decision lever

The question is not whether a cash balance plan saves tax — at $300,000 net and age 52 it defers roughly $52,500–$70,000 in federal tax in year one, and that is settled by the §415 and §404 math. The question is whether your income is stable enough to honor a multi-year §412 funding obligation. If you can answer “yes, my net income has cleared $250,000 for several years and I expect it to continue,” the cash balance plan is the highest-leverage tax move available to a solo professional once the $72,000 Solo 401(k) is full. If your income is lumpy, max the Solo 401(k), bank the cash, and revisit the pension the year your income becomes predictable.