What a cash balance plan actually is

A cash balance plan is a flavor of defined-benefit pension plan. Legally it sits in the same IRS bucket as a traditional pension — your business is the sponsor, and the sponsor promises a benefit at retirement. Functionally, though, it looks like a personal account. The plan document specifies an annual pay credit (a stated dollar amount or percentage of compensation that gets credited each year) plus an interest credit (often pegged to the 30-year Treasury or a fixed rate like 5%). Over time the participant — you, the physician owner — accrues a notional account balance that can be paid as a lump sum at termination of the plan or rolled to an IRA.

The reason physicians care is the tax shelter. A solo 401(k) caps you at the defined-contribution limit (employee deferral plus employer profit-sharing); for 2026 that is in the mid-$70,000 range for a participant under 50, and roughly the high-$80,000 range with catch-up. A cash balance plan opens an entirely separate defined-benefit limit that, at the right age and income, can shelter another $150,000 to $300,000 or more on top of the 401(k). For a high-earning solo physician in a high-tax state, that is real money — often six-figure annual federal-and-state tax savings.

Age-based contribution limits (2026 ballpark)

Cash balance contribution limits are not a single number. They are computed actuarially against the IRC §415(b) maximum benefit at retirement, with current-year contributions sized to fund that benefit over your remaining working years. Two practical consequences:

• Older physicians can shelter more, because there are fewer years to fund the same maximum benefit.
• You cannot run a cash balance plan for a single year and then turn it off without consequence — the IRS expects you to operate it for at least a few years, typically three or more, before terminating.

For planning purposes only — confirm your actual maximum with a credentialed actuary — here is a rough age curve a TPA might quote for a solo physician with strong, stable W-2-style or net-self-employment income above the contribution targets:

Age	Approx. cash balance contribution	Approx. total stack (CBP + 401(k))
40	$95k–$130k	$170k–$210k
45	$130k–$170k	$205k–$250k
50	$180k–$230k	$265k–$320k
55	$230k–$300k	$320k–$395k
60	$300k–$355k	$390k–$455k
65	$340k–$400k	$430k–$500k

These are planning ranges, not promises. The actual ceiling depends on the plan's pay credit formula, the interest crediting rate, the actuarial assumptions, and your W-2 or net-self-employment income. Anyone who quotes you a single number without running an actuarial projection is selling, not advising.

How a solo physician stacks 401(k) + cash balance

The textbook stack for an unincorporated solo physician — or a single-member PLLC taxed as a sole proprietor — looks like this in 2026:

1. Employee 401(k) deferral. You defer the IRS elective deferral limit from your wages or owner draw equivalent. Catch-up if you are 50+.
2. Employer profit-sharing. The business contributes up to the defined-contribution ceiling for the year, minus your employee deferral. For a self-employed physician, this is computed on net self-employment earnings after the deductible half of SE tax.
3. Cash balance contribution. The actuarial annual contribution to the cash balance plan, paid by the business as a separate plan contribution.

Two structural rules to know. First, when you add a cash balance plan, the profit-sharing piece of the 401(k) is typically capped at 6% of eligible compensation because the IRS does not let you "double up" the full defined-contribution limit while also running a separate defined-benefit plan. Second, the cash balance contribution itself is a business deduction — it lowers your Schedule C net profit (and therefore your QBI, your self-employment tax base, and your AGI). For a physician in the 32–37% federal bracket plus state, the after-tax cost of a $200,000 contribution can be in the $100,000–$120,000 range.

Real costs — actuary, TPA, audit

A solo cash balance plan is not free to operate. Expect roughly:

• Plan design + actuarial setup: $1,500–$3,500 one-time.
• Annual TPA + actuarial fee: $2,500–$5,000 per year for a solo plan; more if a spouse is also a participant or the plan covers W-2 staff.
• Form 5500 filing: bundled into the TPA fee in most cases.
• Investment custody: low-basis-point ETF custody at a brokerage; budget under $200/year for a solo plan.
• PBGC premiums: generally not applicable to professional-service-employer plans covering only owners (a regulatory carve-out), but verify with your TPA.

On a $200,000 annual contribution at 32% combined marginal rate, $4,000 of admin cost is 2% of the contribution and roughly 6% of the tax savings — usually well worth paying. At a $50,000 contribution it is closer to 8% of the contribution and 25% of the tax savings, which is when the math starts to stop working.

When the math stops working

Three real-world scenarios where a solo physician should pause before adopting (or should consider terminating) a cash balance plan:

1. Income volatility. A locum-heavy schedule with $400k one year and $180k the next makes a cash balance plan painful — the required actuarial contribution does not flex down freely.
2. Hiring W-2 staff. Once you have a non-spouse W-2 employee, the plan must satisfy nondiscrimination testing. A skilled TPA can usually design around this with a cross-tested allocation that still favors the owner, but the staff cost is real.
3. Tax-rate compression. If your marginal rate is going to fall sharply in retirement (e.g., moving from a 9.3% state to a no-income-tax state), the value of an upfront deduction at 37%+ for a future withdrawal at 24% is large; if your rate will not fall much, the value shrinks.

How a solo physician actually sets one up

1. Decide on entity. A single-member PLLC or sole proprietorship is usually fine; an S-corp adds complexity (the S-corp pays you W-2 wages, and the cash balance allocation is computed on those wages, not on K-1 income).
2. Run a projection. Ask a TPA for a no-obligation projection at your age, income, and ideal contribution. Get two quotes — quoted contribution ranges should be within 10–15% of each other.
3. Choose investments. A simple 60/40 indexed portfolio inside the plan is typical. The plan's interest credit (often 4–5% fixed) is what counts for participant accrual; investment performance above the credit is the sponsor's; below is the sponsor's risk.
4. Adopt + fund. Plans must be adopted by the business's tax year-end (and in many cases can be adopted up to the extended tax return deadline for the prior year, per SECURE Act flexibility — confirm with your CPA).
5. Operate. Make the actuarial-calculated contribution every year, file Form 5500 annually, review the plan every 3–5 years.

The cash balance plan is one of the highest-leverage tax tools available to a solo-practice U.S. physician at attending-level income — and it is meaningfully more powerful in the second half of a career, where the age-based limits scale up. It also has the highest setup-and-operate cost of anything in the physician-finance toolkit, so the math has to be honest. For the broader physician picture, start with our Physician Passive Income Guide, and pair this with our physician mortgage guide and own-occupation disability insurance guide so the full balance sheet — assets, leverage, income protection — is built deliberately.

Frequently asked questions