Retirement Plan Design Is a Tax Strategy. Most Dental Practices Treat It Like a Checkbox.

Most dental practice owners end up with a SEP-IRA because someone set it up fast before a tax deadline. That is not a strategy. That is a default, and defaults are rarely optimal.

Retirement plan design is one of the most powerful, permanently recurring tax levers available to a practice owner. Unlike a one-time deduction, the right plan compounds in your favor for decades. The wrong one, or simply the convenient one, leaves meaningful money on the table every single year.

The Three Structures You Need to Understand

Before comparing them, understand what each plan actually is.

The SEP-IRA is the simplest. Contributions are made solely by the employer, as a percentage of compensation, up to an annual IRS ceiling. There is no employee contribution, no Roth option, and no catch-up contribution. You can open one retroactively, even after year-end, which is why accountants reach for it under deadline pressure. It is flexible (you can contribute nothing in a lean year) and administratively cheap. It is also the least powerful tool in the box for a high-income owner who wants to shelter significant income.

The Solo 401(k) is available only to businesses with no full-time W-2 employees other than the owner and a spouse. It has two buckets: an employee elective deferral and an employer profit-sharing contribution. The combination of both buckets means a solo dentist or owner-only practice can often reach the IRS annual addition limit at a lower income level than a SEP-IRA requires. It also allows Roth contributions and catch-up contributions for owners over fifty, two features the SEP-IRA does not offer. The trade-off is more administrative structure, including annual Form 5500-EZ filing once plan assets cross a threshold.

Defined benefit and cash balance plans operate differently from defined contribution plans. Instead of targeting a contribution amount, these plans target a benefit at retirement and work backward to fund it. Annual actuarial calculations determine the required contribution, which can be substantially higher than what any 401(k) or SEP-IRA allows. For an older, high-income owner with fewer years to retirement, the contribution levels can dwarf anything a defined contribution plan permits. The trade-off is real: these plans are complex, require an actuary, carry minimum funding requirements, and are generally inflexible in lean years. If you set one up and income drops, you may still be required to fund it at a prescribed level.

Who Tends to Fit Each Structure

The right plan is a function of four variables: income level, age, whether you have employees, and what you are actually trying to accomplish.

SEP-IRA tends to fit when:

• The practice is early-stage and income is variable
• Simplicity and flexibility matter more than maximizing shelter
• You have W-2 employees, because the SEP requires you to contribute the same percentage for eligible employees as you contribute for yourself, which sharply raises the cost of high contribution rates
• You want administrative simplicity without ongoing plan documents

Solo 401(k) tends to fit when:

• You have no full-time W-2 employees other than yourself (and possibly a spouse)
• You want to maximize the contribution at a lower income level than the SEP requires to hit the same ceiling
• You want access to Roth treatment or catch-up contributions
• You are a specialist or associate-to-owner transition, or a practice owner who runs a lean single-provider model

Defined benefit or cash balance tends to fit when:

• You are in your forties or fifties and want to compress decades of retirement saving into fewer years
• Practice income is high and relatively stable
• You have already maxed a 401(k) and want additional pre-tax shelter well beyond what defined contribution limits allow
• You can tolerate required minimum contributions even in softer revenue years
• You have employees but have modeled the cost and the math still favors the plan

Many high-income practices combine structures. A cash balance plan layered on top of a 401(k) profit-sharing plan is a common design for older owners with stable production. The 401(k) handles the employee benefit; the cash balance absorbs the owner's maximum shelter. The two work together, and the combined annual deduction can be substantial relative to what either plan allows alone.

The Employee Factor Changes Everything

This point deserves its own section because it surprises a lot of dentists.

The moment you have full-time W-2 employees, the SEP-IRA's simplicity becomes expensive. You cannot contribute aggressively for yourself without contributing the same percentage for all eligible employees. At high contribution rates, this cost can erode most of the tax benefit the owner was trying to capture.

The Solo 401(k) closes completely once you hire full-time employees outside the owner-spouse structure. At that point, you are in plan-design territory, and the decision becomes: a SIMPLE IRA, a Safe Harbor 401(k), a traditional 401(k) with discrimination testing, or a more complex layered design.

Defined benefit plans require contributions for eligible employees as well, but the owner's benefit formula can be structured to deliver disproportionately large contributions on the owner's behalf, particularly when the owner is significantly older than the average employee. The actuarial math works in the older owner's favor here.

None of this is a reason to avoid hiring. It is a reason to design the plan before you hire, not after.

Why Most Practices Default Instead of Design

Three reasons.

First, retirement plan conversations happen near tax deadlines, when the accountant is in triage mode and the easiest answer is the one that can be executed in a day.

Second, the financial advisor who would benefit from a plan recommending a specific structure is not always the same person as the CPA who understands the tax mechanics of that structure. Each professional sees half the picture.

Third, dentists frequently underestimate how much practice income they will earn at peak production and how compressed the window is between peak earning and the age at which they want to sell. The plan that made sense at thirty-five is often wrong at forty-eight.

The time to design a retirement plan is when income becomes predictable and significant, not when a deadline forces the issue.

Practical Questions Worth Asking Your Advisor

• What is my current plan costing me in foregone tax savings relative to what a better-designed plan would deliver?
• If I add a cash balance or defined benefit layer on top of my existing plan, what is the range of additional deduction available given my age and income?
• What does my employee census look like, and how does it affect the cost of funding employee benefits at various contribution rates?
• Am I using catch-up contributions if I am fifty or older?
• Is my current plan design consistent with where I expect income to be in the next three to five years?

A retirement plan review is not a complex project. A good CPA and a qualified ERISA advisor can model the options in a focused engagement. The output is a decision, not a default.

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FAQ

Can I have both a 401(k) and a SEP-IRA in the same year? Generally no, not for the same business. The IRS rules on combining plan types are specific and depend on the plan year and contributions already made. Get current guidance before attempting this.

How often should I revisit my plan design? At minimum, any time income changes materially, you add or lose employees, you turn fifty, or you begin thinking seriously about a sale or transition timeline. Annual is not excessive.

Is a cash balance plan right for me if I might sell in five years? Maybe. The plan can be terminated, but there are rules, costs, and timing considerations. The sale timeline should be part of the design conversation, not a surprise at the end.

What is the role of the financial advisor versus the CPA here? The CPA models the tax impact. The advisor handles investment selection and plan administration. Both need to be in the same room, or at minimum the same conversation. When they are not, gaps in the design often follow.

This article is general educational information, not tax or legal advice. Consult a qualified tax advisor regarding your specific situation before making retirement plan decisions.