Dental Practice 401(k) Plan: Setup Guide for Practice Owners (2026)

Your solo 401(k) worked great when you were the only employee. The day you hire a full-time W-2 associate, you lose solo 401(k) eligibility — and you need a group plan. Done right, a safe harbor 401(k) lets you still shelter up to $72,000 per year in your own account (or $80,000 with catch-up contributions), while satisfying IRS nondiscrimination rules, qualifying your practice for a startup tax credit, and becoming a meaningful recruiting tool for quality associate candidates.

The trigger: when solo 401(k) eligibility ends

A solo 401(k) — sometimes called a one-participant 401(k) or owner-only 401(k) — is only available to business owners with no full-time W-2 employees other than a spouse. For IRS purposes, "full-time" generally means an employee who worked more than 1,000 hours in the previous plan year.

Once you hire an associate or any other W-2 employee who crosses the 1,000-hour threshold, you must offer a plan that covers eligible employees under the same rules that apply to you. Continuing to contribute only to a solo 401(k) at that point puts the plan out of compliance — a problem that can trigger excise taxes and required corrective distributions.

Plan options for dental practices with employees

For most dental practices with associates and support staff, the safe harbor 401(k) is the right answer. It eliminates the ADP/ACP nondiscrimination testing that trips up owner-heavy practices, and lets you maximize profit sharing on top of employee deferrals to hit the §415(c) total limit.

Safe harbor 401(k): how it works for dental practices

A safe harbor 401(k) automatically passes ADP and ACP nondiscrimination tests in exchange for meeting one of three employer contribution formulas. You choose the formula at plan adoption; it can be changed annually with proper notice.

The three safe harbor formulas

Maximizing your own contribution in a group plan

The owner can contribute as both employee and employer, hitting the §415(c) ceiling. In 2026, that's $72,000 (or $80,000 with age-50+ catch-up; $83,250 with the ages-60–63 SECURE 2.0 super catch-up).¹

The path to $72,000 as a practice owner on an S-corp payroll of $150,000:

• Employee deferral: $24,500
• Employer profit sharing: 25% of W-2 salary = $37,500
• Total: $62,000 — leaving $10,000 of room that could be filled with a layered cash balance plan

Higher W-2 salary unlocks more profit sharing, up to the §401(a)(17) compensation limit of $360,000 in 2026. The practical ceiling on profit sharing is $47,500 ($72,000 − $24,500), which requires a W-2 of at least $190,000 for the 25%-of-comp formula to produce that amount.¹

What it actually costs to run the plan

Plan costs for a dental group 401(k) typically break into three buckets:

Even with $5,000 in annual plan costs and $16,200 in required employer contributions, the owner's deduction on $72,000 of personal contributions at a 37% federal rate saves $26,640 in taxes — a strongly positive ROI from day one.

SECURE Act startup tax credit: the government pays most of the setup cost

If your dental practice has never offered a retirement plan before and has fewer than 100 employees, you qualify for a startup tax credit that covers:

• 50–100% of plan startup costs for each of the first three plan years
• Practices with fewer than 50 employees can claim up to 100% of eligible startup costs
• Credit calculated as $250 × the number of non-highly-compensated eligible employees (NHCEs), up to a maximum of $5,000 per year
• A separate $500 automatic-enrollment credit is available if the plan includes auto-enrollment (QACA or EACA design)²

A practice with 4 eligible staff (NHCEs) would qualify for a $1,000 credit per year for three years — enough to cover TPA costs entirely.

The 2026 auto-enrollment requirement for new plans

Under SECURE 2.0, new 401(k) plans established after December 29, 2022 must include automatic enrollment for eligible employees, starting at an initial deferral rate of at least 3%, increasing by 1% per year to a minimum of 10%. This applies to new plans — existing plans established before that date are grandfathered.²

For dental practices setting up their first group plan in 2026, automatic enrollment is required. In practice, this is straightforward: most modern 401(k) platforms handle it automatically. And it helps — employees who are enrolled automatically tend to stay enrolled, which improves overall plan participation and can help nondiscrimination testing even beyond the safe harbor floor.

SIMPLE IRA: the lower-cost alternative for early-stage practices

If your practice has 100 or fewer employees and you want the simplest possible plan, a SIMPLE IRA is worth considering — but understand the tradeoffs.

A SIMPLE IRA makes sense for a practice with 1–2 employees and an owner who earns under $200,000 — the contribution ceiling is less painful at lower income levels. For any practice owner netting $250,000+, the $55,000 gap between SIMPLE IRA and safe harbor 401(k) annual maximums translates directly to $20,000+ per year in lost tax deferral. Upgrade to a group 401(k) as soon as the math supports it.

Layering a cash balance plan on top

A group safe harbor 401(k) can be combined with a cash balance defined benefit plan, just like a solo 401(k) can. The §415(b) and §415(c) limits are separate, so both plans fund simultaneously. For a practice owner age 50–60 netting $400,000+, this combination is the highest-deduction option available — sheltering $150,000–$265,000 per year depending on age and plan design.

The employee coverage requirement for cash balance plans is more complex than for 401(k) plans. The TPA must model nondiscrimination under the general test (or cross-testing) before layering a cash balance plan onto a group 401(k). For practices with a mix of owner-doctors and lower-compensated staff, this typically works — the math is just more involved.

How to choose a TPA for your dental practice plan

The TPA (Third Party Administrator) handles plan document drafting, annual nondiscrimination testing (even with safe harbor), Form 5500 filing, and participant notices. For dental practices, a few criteria matter:

• Experience with professional practice plans. Dental and medical practices have unusual compensation structures (W-2 salary on S-corp, associate percentage arrangements). A generalist TPA may not understand the nuances.
• Actuarial capability if you plan to layer a cash balance plan. Not all TPAs have credentialed actuaries in-house.
• Transparent flat-fee pricing. Asset-based fees grow as your balance does — for a practice where the owner's account will hit $1M+ over a decade, flat fees are usually better.
• Integration with your payroll provider. Automated payroll integration reduces manual contribution errors and simplifies compliance.

Implementation timeline

1. Assess the trigger. Confirm that you have or will have a W-2 employee crossing the 1,000-hour threshold this plan year. Engage a TPA before year-end if that's the case.
2. Choose your safe harbor formula. Typically 3% non-elective for most dental practices. Your advisor and TPA will model the cost for your specific staff compensation levels.
3. Decide on auto-enrollment design. New plans must include it; design the initial deferral rate (3% starting is the legal minimum for required auto-enrollment).
4. Sign the plan document by December 31. The plan must be formally established by year-end to allow contributions for that tax year.
5. Notify employees. Safe harbor notice must go to employees 30–90 days before the plan year begins.
6. Set up payroll integration. Coordinate with your payroll provider to automate deferrals and employer contributions each payroll cycle.
7. Claim the startup tax credit. File Form 8881 with your practice tax return to capture the SECURE Act credit in the first three years.