Dental Practice Retirement Plans: Defined Benefit, Cash Balance, Solo 401(k), and How to Stack Them

A dentist earning $400,000+ has one tax lever bigger than every entity trick and deduction combined: qualified retirement plans. Designed well, a practice owner in their 50s can defer $150,000–$300,000+ per year, deduct every dollar, and do it while providing a legitimately good benefit to staff. Designed badly, the same owner funds an expensive plan where most of the money goes to everyone except them. The difference is plan design, and dentistry — small staff, high owner income, big owner-staff age gap — is the ideal demographic for the aggressive designs.

Key takeaways

• For 2026, 401(k) employee deferrals are $24,500 (plus $8,000 catch-up at 50+, and a larger catch-up at ages 60–63), and the total defined-contribution limit is $72,000 per person before catch-ups.
• A "Solo" 401(k) only works with no employees other than a spouse. The moment you have an eligible hygienist, you need a real plan.
• Safe harbor 401(k) plus cross-tested profit sharing is the workhorse design: it maxes the owner while staff cost typically runs 5–7.5% of their pay.
• A cash balance plan stacked on top can add anywhere from ~$100,000 to $300,000+ of deductible owner contributions per year depending on age.
• Cash balance plans are multi-year commitments with required annual funding — they fit stable, consistently profitable practices, not volatile ones.

Start with the 2026 numbers

The defined-contribution side for 2026: employee elective deferrals of $24,500; catch-up of $8,000 for age 50+ (with an enhanced catch-up of $11,250 for those aged 60–63); combined employee-plus-employer limit of $72,000; and compensation counted up to $360,000. High earners take note: catch-up contributions for those earning over $145,000 (indexed) must now be Roth.

SEP-IRAs share the $72,000 ceiling but have a fatal flaw for practices with staff: whatever percentage of compensation you contribute for yourself, you must generally contribute for every eligible employee. A 20% SEP contribution for the owner means 20% for the hygienist and both assistants. SEPs are fine for a moonlighting associate's 1099 income; they're the wrong tool for a practice.

Why the Solo 401(k) headline doesn't apply to you

The Solo (one-participant) 401(k) lets an owner-only business hit the full $72,000 with modest income, because the owner wears both hats — employee deferral plus 25% employer contribution. The catch is in the name: one participant. Employees who meet eligibility (which, post-SECURE 2.0, includes long-term part-timers with two consecutive years of 500+ hours) must be allowed in, and then it's not a solo plan anymore. A practice with even a part-time front desk person is generally outside solo territory. Where it does fit dentists: 1099 specialty income earned genuinely outside the practice, or a spouse-only consulting entity — with care that the businesses aren't a controlled group, which would pull practice staff back in.

The workhorse: safe harbor 401(k) + cross-tested profit sharing

The standard design for a real dental office has three layers:

1. 401(k) deferrals — the owner defers the maximum ($24,500 / $32,500 with catch-up).
2. Safe harbor contribution — typically a 3% non-elective contribution to all eligible staff. This buys out the ADP/ACP nondiscrimination tests, which small-staff plans otherwise fail routinely, capping the owner's deferrals.
3. Cross-tested ("new comparability") profit sharing — the design that does the heavy lifting. Instead of testing contribution percentages, cross-testing projects contributions to a benefit at retirement age. Because the owner is usually 15–25 years older than the staff, a dollar contributed for a 55-year-old owner projects to a much smaller retirement benefit than a dollar for a 28-year-old assistant — so the owner can receive a dramatically higher contribution percentage and still pass testing. Typical outcome: owner receives the full remaining amount up to the $72,000 cap while staff receive a "gateway" contribution of 5% (sometimes up to 7.5%) of pay.

Illustrative math for a 55-year-old owner with $360,000 of plan compensation and four staff earning $250,000 combined: owner puts away $72,000 + $8,000 catch-up = $80,000, fully deductible; staff cost roughly $12,500–$18,000, also deductible; total owner benefit relative to staff cost is the ratio that makes the design worth its ~$2,500–$4,500 annual administration fee. The older the owner and younger the staff, the better it works.

The second story: cash balance plans

When the DC plan is maxed and the owner still wants deductions, the answer is a defined benefit plan — almost always in its modern "cash balance" form, where each participant has a hypothetical account credited annually with a pay credit and a guaranteed interest credit. Because DB limits are set by the benefit at retirement (a life annuity of up to $290,000/year for 2026), the older the participant, the more that can be contributed now to fund it. Rough annual pay-credit capacity: a dentist at 45 might contribute $150,000–$180,000; at 55, $250,000–$300,000+; at 60, more still — on top of most of the 401(k) layer.

Stacking rules to know: when an employer sponsors both a DB and a DC plan (and the DB plan isn't PBGC-covered — small professional-practice plans usually aren't), the combined deduction rules effectively limit the employer DC contribution to 6% of compensation if you want the full DB deduction — which is why stacked designs pair the cash balance plan with 401(k) deferrals plus a 6% profit sharing layer rather than the full cross-tested amount. Your TPA runs this; you just need to know the full-throttle profit sharing and full-throttle cash balance don't stack unrestricted.

The commitments are real: cash balance plans have required minimum funding each year — this is not a "contribute if it was a good year" arrangement. The IRS expects permanence (informally, plan to run it at least 3–5 years). Assets are invested to a conservative target matching the interest-credit rate, because outperformance doesn't increase your benefit and underperformance increases required contributions. And staff must be covered here too, typically at a modest pay-credit level layered into the combined testing.

Who fits: a dentist 45+, consistently netting $500,000+, with stable cash flow, a 10-to-20-year runway, and an appetite to convert current 37%-bracket income into deferred savings. Who doesn't: volatile practices, owners within a year or two of a DSO sale (plan termination mid-stride is messy), and anyone who flinches at a mandatory mid-six-figure annual contribution.

Deadlines, credits, and Roth angles

Post-SECURE, a new plan can be adopted up to the extended due date of the return for the year — meaning a great year discovered at tax time in 2027 can still get a 2026 profit-sharing or cash balance plan (employee deferrals can't be retroactive; those need the plan in place during the year). Startup tax credits under SECURE 2.0 can cover up to 100% of small-employer plan administration costs (capped) for the first three years, plus a credit for employer contributions to staff — for a typical dental office, the first years of a new 401(k) are close to free. Roth options (Roth deferrals, and now Roth employer contributions if the document allows) trade today's deduction for tax-free growth — usually the right call for young associates in the plan and the wrong call for the peak-bracket owner, which is fine, because each participant chooses.

Official sources

• IRS — Retirement plan contribution limits (COLA table): https://www.irs.gov/retirement-plans/cola-increases-for-dollar-limitations-on-benefits-and-contributions
• IRS — One-participant 401(k) plans: https://www.irs.gov/retirement-plans/one-participant-401k-plans
• IRS — Cash balance plan overview: https://www.irs.gov/retirement-plans/defined-benefit-plan
• IRS — Retirement plans startup costs tax credit: https://www.irs.gov/retirement-plans/retirement-plans-startup-costs-tax-credit

Practitioner note: Ask any plan proposal two questions: "What percentage of total contributions lands in my account?" (well-designed dental plans typically run 85–92%) and "What's my required contribution in a bad year?" If the salesperson answers the first and dodges the second, you're looking at a cash balance illustration built for the best case only.

Fairlight coordinates plan design with your TPA and actuary, models the owner-vs-staff allocation on your real census, and handles the payroll and deduction mechanics — including cross-border wrinkles for dentists with Canadian retirement accounts in the picture. Contact us or see pricing.