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The Overview
For most physicians, retirement plans are one of the most consequential parts of a tax plan, and one of the most underused.
The right plan design at physician income levels can shelter substantial amounts from current year tax. The wrong setup leaves significant contribution capacity unused, and the gap compounds over a career.
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This guide walks through every retirement plan that matters for physician retirement tax planning: Solo 401(k), employer 401(k) and 403(b), cash balance plans, the backdoor Roth IRA, and the mega backdoor Roth. It covers how to combine them, what the rules say, and where physicians lose the most money to avoidable mistakes.
In This Guide
Why It Matters
Why Retirement Plans Are the Most Powerful Tax Tool You Have
A physician at the 32% federal bracket who shelters $70,000 in a Solo 401(k) keeps $22,400 in federal tax that would otherwise leave the household. Add state tax at 5% to 10% and the same contribution returns $25,900 to $29,400 in current year savings, with the contributed dollars growing tax-deferred for decades. The exact federal savings on each contribution dollar depend on your marginal bracket. For the bracket-by-bracket breakdown at physician income levels, see our physician tax brackets guide.
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Retirement plans work as a tax tool because the contribution is deducted directly from taxable income, the dollar limits are large at physician income levels, and a properly designed plan stack can reach total annual contributions in the $200,000 to $370,000 range, depending on age, entity structure, and plan design.
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The catch is that the rules are not trivial. The wrong plan choice in your 30's can cost you a backdoor Roth in your 40's. A SEP IRA opened to "keep it simple" can permanently cap your contributions below what a Solo 401(k) would allow. This is the layer of proactive tax planning for physicians that compounds across an entire career.
Picking Your Plan
Solo 401(k) vs. SEP IRA: Why Solo 401(k) Usually Wins
For a physician with self employment income (locum tenens, 1099 contracting, expert witness work, consulting, or an S-Corp practice), the choice between a Solo 401(k) and a SEP IRA is one of the most consequential retirement decisions you will make. In nearly every case, the Solo 401(k) is the better option.
SEP IRA
Solo 401(k)
Feature
Triggers the pro rata rule on Roth conversions
Compatible. Not an IRA, so no pro rata rule exposure
Backdoor Roth compatibility
None
Form 5500-EZ once plan assets exceed $250,000
Annual IRS filing
Tax filing deadline, including extensions
December 31 of the tax year
Plan establishment deadline
Not allowed
Up to $50,000 if the plan document allows
Loan provision
No
Yes, on the employee deferral
Roth contribution option
Capped by the 25% employer share alone
415(c) annual limit, approximately $69,000 to $70,000 in recent years
Total contribution ceiling
Up to 25% of W-2 compensation (or 20% of net self-employment income for sole proprietors)
Up to 25% of W-2 compensation
Not allowed
Approximately $23,500, plus $7,500 catch-up at age 50+
Employer profit sharing
Employee elective deferrals
The table makes two things clear:
1
First, at the same income level, a Solo 401(k) almost always lets you contribute more, because you get both the employee deferral and the employer share rather than just the employer share.
2
Second, a Solo 401(k) leaves the door open to a clean backdoor Roth, and a properly designed Solo 401(k) opens the door to a mega backdoor Roth as well.
A SEP IRA closes both doors.
The single advantage of a SEP IRA is administrative simplicity, including the ability to establish and fund retroactively up to your tax filing deadline with extensions. A Solo 401(k) must be established by December 31. For the physician who only thinks about retirement contributions in April, that is the default that locks them into a SEP IRA. For more on the IRA pro rata problem this creates, see our blog post on the SEP-IRA trap.
Picking Your Plan
Solo 401(k) vs. SEP IRA: Why Solo 401(k) Usually Wins
For a physician with self employment income (locum tenens, 1099 contracting, expert witness work, consulting, or an S-Corp practice), the choice between a Solo 401(k) and a SEP IRA is one of the most consequential retirement decisions you will make. In nearly every case, the Solo 401(k) is the better option.
SEP IRA
Solo 401(k)
Feature
Triggers the pro rata rule on Roth conversions
Compatible. Not an IRA, so no pro rata rule exposure
Backdoor Roth compatibility
None
Form 5500-EZ once plan assets exceed $250,000
Annual IRS filing
Tax filing deadline, including extensions
December 31 of the tax year
Plan establishment deadline
Not allowed
Up to $50,000 if the plan document allows
Loan provision
No
Yes, on the employee deferral
Roth contribution option
Capped by the 25% employer share alone
415(c) annual limit, approximately $69,000 to $70,000 in recent years
Total contribution ceiling
Up to 25% of W-2 compensation (or 20% of net self-employment income for sole proprietors)
Up to 25% of W-2 compensation
Not allowed
Approximately $23,500, plus $7,500 catch-up at age 50+
Employer profit sharing
Employee elective deferrals
The table makes two things clear:
1
First, at the same income level, a Solo 401(k) almost always lets you contribute more, because you get both the employee deferral and the employer share rather than just the employer share.
2
Second, a Solo 401(k) leaves the door open to a clean backdoor Roth, and a properly designed Solo 401(k) opens the door to a mega backdoor Roth as well.
A SEP IRA closes both doors.
The single advantage of a SEP IRA is administrative simplicity, including the ability to establish and fund retroactively up to your tax filing deadline with extensions. A Solo 401(k) must be established by December 31. For the physician who only thinks about retirement contributions in April, that is the default that locks them into a SEP IRA. For more on the IRA pro rata problem this creates, see our blog post on the SEP-IRA trap.
Don't Leave It on the Table
Maximizing Your Employer 401(k) or 403(b)
Most attending physicians have access to an employer 401(k) or 403(b), and many do not maximize what their plan offers beyond the basic deferral.
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The employee elective deferral limit is shared across all 401(k) and 403(b) plans you participate in during a single year. You cannot put $23,500 in a hospital 403(b) and another $23,500 in a Solo 401(k) for moonlighting income. The employer match and profit sharing contribution, however, are calculated per plan, which is why a W-2 physician with side 1099 income can stack significant employer contributions across two plans.
Three questions are worth asking your benefits department or your tax team:
1
Does your plan offer after tax employee contributions? If yes, you may be eligible for a mega backdoor Roth (covered below). Many physicians have this option and never use it because no one told them it existed.
2
Does your plan allow in service Roth conversions or in service withdrawals? This is the second half of what makes a mega backdoor Roth work.
3
Is there a 457(b) plan available? Hospital systems and academic medical centers often offer a governmental 457(b) alongside the 403(b), with its own separate deferral limit that effectively doubles your employee contribution capacity. Non-governmental 457(b) plans carry different (and often unfavorable) creditor and distribution rules.
If your spouse also works, coordinating plan participation across both employers can add another $30,000+ in annual tax deferred savings, which becomes especially powerful for dual physician households at combined incomes of $500,000+.
The Largest Deduction
Cash Balance Plans: A Defined Benefit Layer on Top of Your 401(k)
A cash balance plan is a defined benefit pension plan with a 401(k) style account presentation. For high income physicians age 45 and older, it allows the largest annual tax deductible contributions of any retirement plan commonly available.
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Annual contribution limits are not fixed dollar amounts. They are actuarially determined based on age, target retirement benefit, compensation, and investment return assumptions. The older the participant, the larger the contribution that can be justified.
Age 40
Approximately $80,000 to $120,000
age 50
Approximately $150,000 to $220,000
age 60
Approximately $200,000 to $300,000+
These contributions sit on top of the Solo 401(k) or employer 401(k) limits. They are tax deductible to the practice or sole proprietorship, grow tax deferred, and are typically rolled to an IRA or 401(k) at termination.
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Cash balance plans are not for everyone.
They require:
1
Stable, reasonably high income. The plan creates a funding obligation. A 1099 physician whose income drops sharply may struggle to meet required contributions.
2
An actuary. Plan design and annual valuations require an actuary, plus Form 5500 filing. Annual administrative costs typically run $2,000 to $5,000+.
3
Coordination with your 401(k). In a private practice with staff, the plan must satisfy nondiscrimination testing alongside the 401(k), which usually requires meaningful staff contributions.
4
Establishment by December 31. Like a Solo 401(k), the plan must be in place before year end. Contributions can be made up to the tax filing deadline.
For physician practice owners and high earning 1099 physicians, a cash balance plan added at the right age can produce six figure annual tax deductions.
Step by Step
The Backdoor Roth IRA, Step by Step
The backdoor Roth IRA is how high income physicians get money into a Roth account despite earning above the direct Roth IRA contribution limit. It is a two step transaction, tax free when executed correctly, and a surprise tax bill when executed without understanding the pro rata rule.
The mechanics:
1
Contribute to a traditional IRA on a non-deductible basis. Because your income exceeds the deduction phase-out, the contribution is non-deductible (after-tax dollars). The current annual contribution limit is approximately $7,000, with a $1,000 catch-up at age 50+.
2
Convert the traditional IRA balance to a Roth IRA. Since the contributed dollars were already taxed, the conversion of just that contribution is tax free.
The trap is the pro rata rule.
The IRS treats all of your traditional IRAs (including SEP and SIMPLE IRAs) as a single pool. If that pool contains pre-tax dollars from a prior 401(k) rollover, an old SEP IRA, or any deductible IRA contribution, the conversion is taxed proportionally based on the ratio of pre-tax to after-tax dollars. A physician with $94,000 in pre-tax IRA balances who tries a $7,000 backdoor Roth conversion ends up with a conversion that is roughly 93% taxable, not tax free.
The fix, in most cases, is to roll the pre-tax IRA balance into a current employer 401(k) or 403(b) (if the plan accepts incoming rollovers) before completing the conversion. Once the IRA balance is at zero, the conversion is clean. For self employed physicians, this is the single most important reason to choose a Solo 401(k) over a SEP IRA: a SEP IRA is a traditional IRA, a Solo 401(k) is not.
Three additional rules that catch physicians off guard:
1
Spousal accounts are calculated separately, so one spouse with a clean balance can backdoor while the other works to clear theirs.
2
The pro rata calculation uses the December 31 balance of all your traditional IRAs in the conversion year.
3
Form 8606 must be filed in the year of every non-deductible contribution, or the documentation problem compounds every year afterward.
Beyond the Basics
The Mega Backdoor Roth: How After Tax 401(k) Contributions Convert to Roth
The mega backdoor Roth is a separate approach from the standard backdoor Roth, and substantially larger. It uses after tax employee contributions to a 401(k) plan, followed by an in plan Roth conversion or in service distribution to a Roth IRA.
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The math works because of the 415(c) annual additions limit, which has run in the $69,000 to $70,000 range in recent years (higher with catch-up at age 50+). After your standard employee deferrals and employer contributions, any remaining headroom under that cap can be filled with after tax contributions, which then convert to Roth.
A 45 year old physician maximizing both pieces could see something like this:
Employee elective deferral (pre-tax or Roth)
$23,500
Employer profit-sharing contribution
$30,000
After-tax contribution converted to Roth
$16,500
Total Roth dollars created
$40,000+ per year
The mega backdoor Roth requires two specific plan provisions: the plan must allow after tax (non-Roth) employee contributions, and it must allow either in service Roth conversions or in service withdrawals. Without one of those, the after tax dollars sit in the plan and grow taxable, which defeats the purpose. For self employed physicians using a custom Solo 401(k) document, both provisions can be included by design. For W-2 physicians, the answer depends on the employer's plan document, which makes it worth asking your benefits department directly.
The Numbers
Plan Stacking: Real Numbers at Three Career Stages
The contribution capacity of plan stacking shows up when you combine plans rather than treating each in isolation. The scenarios below use approximate IRS limits in recent years; actual numbers vary with annual IRS adjustments, plan design, reasonable compensation, and individual circumstances.
Scenario 1: 40 year old S-Corp physician, $400,000 net income
Reasonable W-2 compensation set at $160,000.
Solo 401(k) employee deferral
$23,500
Solo 401(k) employer profit-sharing (25% of W-2)
$40,000
After-tax contributions to Solo 401(k), converted to Roth
approximately $6,500 (filling the 415(c) limit)
Backdoor Roth IRA
$7,000
Spouse backdoor Roth IRA (if applicable)
$7,000
Cash balance plan (illustrative for age 40)
$90,000
Approximate total tax advantaged contributions
$174,000
Scenario 2: 50 year old S-Corp physician, $500,000 net income
Reasonable W-2 compensation set at $200,000.
Solo 401(k) employee deferral plus catch-up
$31,000
Solo 401(k) employer profit-sharing (25% of W-2)
$50,000
Backdoor Roth IRA with catch-up
$8,000
Spouse backdoor Roth IRA with catch-up (if applicable)
$8,000
Cash balance plan (illustrative for age 50)
$180,000
Approximate total tax advantaged contributions
$277,000
Scenario 3: 55 year old practice owner, $700,000 net income
Reasonable W-2 compensation set at $250,000.
401(k) employee deferral plus catch-up
$31,000
401(k) employer profit-sharing
$50,000
Backdoor Roth IRA with catch-up
$8,000
Spouse backdoor Roth IRA with catch-up
$8,000
Cash balance plan (illustrative for age 55)
$240,000
Approximate total tax advantaged contributions
$337,000
These numbers are illustrative, not promises. They depend on plan design, S-Corp reasonable compensation analysis, physician entity formation, and dozens of other factors. The gap between what most physicians actually contribute and what these scenarios show is the gap that proactive tax planning closes.
A 30 minute conversation with the Doc Wealth tax team will tell you whether your current retirement plan structure is anywhere near what your income allows, and what changes would have the biggest tax impact this year.
What to Avoid
The Mistakes That Cost Physicians the Most
The most expensive retirement tax errors are not exotic. They are the same handful of mistakes, repeated across thousands of returns.
1
Choosing a SEP IRA over a Solo 401(k).
Most self employed physicians who land at a SEP IRA do so because their preparer offered a quick option in April. The choice locks in a lower contribution ceiling and creates a future pro rata problem with the backdoor Roth.
2
Missing the December 31 plan establishment deadline.
Solo 401(k) and cash balance plans must exist by year end. Contributions can come later. The plan document cannot.
3
Triggering the pro rata rule on a backdoor Roth conversion.
Pre-tax IRA balances must be cleared into an employer 401(k) before the conversion year ends.
4
Skipping Form 8606.
Without it, the IRS may treat the entire converted balance as taxable.
5
Underfunding the employer 401(k) match.
Missing the employer match means missing free retirement contributions, and at physician income levels the cumulative cost over a career is significant. This is the most common preventable error among W-2 physicians.
6
Failing to coordinate spousal plans.
Two physicians, two employers, two sets of plan options, and almost no one looks at them together until they engage a physician CPA.
7
Adding a cash balance plan without nondiscrimination analysis.
In a private practice with staff, a plan that fails testing requires corrective contributions or amendments.
For more on year end planning moves that interact with retirement plans, see 5 Tax Moves to Make Before December 31st
Why Doc Wealth
How Doc Wealth Builds Your Retirement Tax Plan
This layer of tax planning gets skipped more often than any other, and the reason is structural. Retirement plan rules sit across plan documents, IRS forms, an actuary you may not know you need, and payroll that has to support whatever you contribute. Coordinating those pieces is not in your training, and it is not in most generalist CPA workflows either.
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Doc Wealth is a physician founded tax planning and preparation firm that works exclusively with physicians. Retirement plan design sits at the center of nearly every plan we build, because for physician income levels it is where the largest legal tax savings live.
For each client, the Doc Wealth tax team:
Reviews current plan participation across all employers and entities, including any spousal plans
Models the optimal stack for the physician's income, age, family structure, and entity setup
Coordinates with actuaries on cash balance plan design where the income, age, and stability profile supports it
Audits IRA balances for pro rata rule exposure and sequences rollovers into employer plans before any backdoor Roth conversion
Confirms that S-Corp reasonable compensation supports the intended employer contribution and survives audit scrutiny
Tracks plan establishment and contribution deadlines so nothing slips through the December 31 or filing deadline gates
Files the required forms (5500-EZ, 8606, and others) accurately and on time
The work happens year round, not at filing time. Plan design and reasonable comp decisions made in the first quarter shape what is possible for the rest of the year.
Q&A
Frequently Asked Questions
01
How much can a physician contribute to retirement plans in a single year?
01
How much can a physician contribute to retirement plans in a single year?
Contributions vary by plan structure and age. A self employed physician with a Solo 401(k) and cash balance plan can stack significant tax deductible contributions across both plans, with totals scaling with age (see the Cash Balance section above for age based contribution ranges). A W-2 physician without self employment income is more limited but can combine a 401(k) or 403(b), a 457(b) where available, and a backdoor Roth.
02
What is the difference between a Solo 401(k) and a SEP IRA for physicians?
02
What is the difference between a Solo 401(k) and a SEP IRA for physicians?
Both allow tax-deductible contributions for self employed income. The Solo 401(k) typically allows higher total contributions, offers a Roth option and loan provisions, and does not interfere with the backdoor Roth. The SEP IRA allows only employer contributions and creates a pro rata problem if you also want a backdoor Roth.
03
What is the pro rata rule and why does it matter for the backdoor Roth?
03
What is the pro rata rule and why does it matter for the backdoor Roth?
The pro rata rule treats all of your traditional IRAs (including SEP and SIMPLE IRAs) as a single pool when you convert dollars to Roth. If the pool contains pre-tax money, the conversion is taxed proportionally. The fix is usually to roll pre-tax IRA balances into a current employer 401(k) before the conversion year ends.
04
Who should consider a cash balance plan?
04
Who should consider a cash balance plan?
Cash balance plans suit high-income physicians, typically age 45+, with stable income, who are already maxing their 401(k). They allow much larger contributions than a 401(k) alone (often $100,000 to $300,000+), but require an actuary, annual administrative costs, and a multi-year commitment.
05
Can W-2 physicians use a backdoor Roth?
05
Can W-2 physicians use a backdoor Roth?
Yes. The backdoor Roth is available regardless of employment type, as long as the pro rata rule is managed. W-2 physicians without pre-tax IRA balances can usually execute a clean backdoor Roth contribution and conversion each year.
06
What is the mega backdoor Roth and who qualifies?
06
What is the mega backdoor Roth and who qualifies?
The mega backdoor Roth uses after-tax 401(k) contributions, converted to Roth, to add tens of thousands in Roth savings beyond the standard employee deferral limit. It requires a 401(k) that allows after-tax contributions and either in-service Roth conversions or in-service withdrawals. Many employer plans lack these features, but a Solo 401(k) can be designed to.
07
When do retirement plans need to be established for the tax year?
07
When do retirement plans need to be established for the tax year?
Solo 401(k) and cash balance plans must be established by December 31. Contributions can typically be made up to the tax filing deadline. SEP IRAs are an exception: they can be both established and funded up to the filing deadline, which is their main practical advantage and the reason many are chosen by default.
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