SEP IRA vs. Solo 401(k) for Physicians With 1099 Income: Which Is Better?

1099 income can start small for a physician – a few moonlighting shifts become a regular side schedule, a medical director role turns into recurring income, or occasional consulting work grows into something substantial enough that leaving all of the money in a checking account no longer makes much sense. Eventually, that additional income creates another decision: Where should the retirement savings go?

For physicians with self-employment income, two of the most common choices are a SEP IRA and a Solo 401(k). Both can create valuable tax-advantaged retirement savings, and both can work alongside income from an employed position, but they aren't interchangeable. The right choice can affect how much of your 1099 income you're able to contribute, whether an existing workplace retirement plan limits your options, how easily you can continue using a Backdoor Roth IRA, and what you may be able to do with old retirement accounts.

For many physicians, the Solo 401(k) offers more flexibility, but that doesn't mean every physician with 1099 income needs one; it means the decision should be made with the rest of your financial life in view.

SEP IRA vs. Solo 401(k) for Physicians: Start With How Your 1099 Income Is Earned

Before comparing contribution limits, it helps to know what income the retirement plan is actually being built around. A physician may receive 1099 income from locums work, moonlighting, expert witness work, consulting, speaking, telemedicine, independent clinical shifts, or another business activity. If that income is reported directly as self-employment income, retirement contributions are generally calculated using adjusted net earnings from self-employment rather than simply taking a percentage of gross 1099 revenue.

That distinction becomes even more important for physicians operating through an S corporation. Retirement contributions for an S corporation owner are based on eligible W-2 compensation, not shareholder distributions. In other words, paying yourself a $100,000 W-2 salary and receiving another $100,000 as an S corporation distribution doesn't give you $200,000 of retirement-plan compensation.

This is one reason retirement-plan decisions shouldn't happen in isolation. The answer can change depending on the amount of 1099 income you're earning, your business structure, whether you have employees, and what retirement benefits are already available through your primary employer.

Once those pieces are clear, the SEP IRA vs. Solo 401(k) comparison gets much easier.

SEP IRA vs. Solo 401(k) Contribution Limits Can Look Very Different

A SEP IRA is funded through employer contributions – there isn't a separate employee salary-deferral component like there is with a 401(k). For 2026, SEP contributions are capped at the lesser of the applicable compensation-based limit or $72,000, although self-employed individuals have to use a special calculation rather than simply multiplying Schedule C profit by 25%.

A Solo 401(k), meanwhile, allows an eligible business owner to contribute in two capacities: employee and employer. For 2026, the employee elective-deferral limit is $24,500 before applicable catch-up contributions. Employer contributions can then be made on top of that, subject to the plan's compensation rules and the overall defined-contribution limit, which is $72,000 for 2026 before catch-up contributions.

That two-part structure is where a Solo 401(k) can become especially powerful for physicians with moderate amounts of 1099 income.

Consider a simplified example of a physician with approximately $50,000 of net self-employment income and no other employee deferrals for the year. 

After the required self-employment adjustments, an employer contribution might be roughly $9,300. A SEP IRA would generally stop there. With a Solo 401(k), the physician may potentially make that employer contribution plus an employee elective deferral, provided the physician still has elective-deferral capacity available. That can create substantially more retirement contribution room from the same amount of side income.

The exact calculation depends on compensation, entity type, self-employment taxes, other retirement plans, and the plan document, so contribution amounts should be calculated rather than estimated from a simple percentage.

A Physician's W-2 Retirement Plan Changes the SEP IRA vs. Solo 401(k) Math

This is where the comparison gets more interesting for physicians. Many physicians don't have only 1099 income – they may earn the majority of their compensation as a W-2 employee while also making meaningful self-employment income on the side.

Suppose a physician is already contributing to a hospital's 401(k) or 403(b). The annual employee elective-deferral limit generally follows the individual across plans, rather than giving the physician a brand-new deferral limit for every 401(k) they open. The IRS specifically notes that someone participating in a 401(k) through a second employer has to consider elective deferrals made across the plans.

If the physician has already used the entire employee deferral through a hospital 403(b), for example, opening a Solo 401(k) doesn't suddenly create another $24,500 of employee deferral space for 2026. The physician may still be able to make an employer contribution based on eligible 1099 business income, however. In that situation, the immediate contribution advantage of a Solo 401(k) over a SEP IRA may become much smaller.

There’s another planning opportunity when the hospital doesn’t provide a matching contribution. Because the physician’s employee elective-deferral limit follows them across plans, there may be less reason to direct all of that deferral through the hospital plan if no employer dollars are attached to it. Depending on the physician’s 1099 income, business structure, and Solo 401(k) terms, some or all of that employee deferral could instead be made through the Solo 401(k), while the physician’s business may also be able to make a separate employer contribution.

That employer contribution can create an additional tax deduction, although the way the deduction is reported depends on how the physician’s business is structured. For example, a sole proprietor generally deducts their own qualified-plan contribution on Schedule 1 rather than treating it as a Schedule C business expense, while an incorporated business may deduct qualifying employer contributions at the business level. The larger point is that a physician whose hospital provides no 401(k) match may have more flexibility in deciding where to use available employee deferrals and how to pair them with employer contributions from 1099 income.

Yet contribution capacity isn't the only reason to compare them.

SEP IRA vs. Solo 401(k): The Backdoor Roth IRA Can Be the Deciding Factor

For high-income physicians, this may be the most important part of the conversation. Many physicians earn too much to make a direct Roth IRA contribution and instead use the Backdoor Roth IRA strategy: making a nondeductible traditional IRA contribution and then converting those funds to a Roth IRA. 

The strategy becomes more complicated when pre-tax IRA money already exists. When Form 8606 determines the taxable and nontaxable portions of an IRA conversion, traditional IRAs are aggregated, and the IRS definition includes SEP IRAs and SIMPLE IRAs. The year-end value of those accounts is part of the calculation.

Imagine a physician has $60,000 sitting in a pre-tax SEP IRA and then makes a $7,500 nondeductible IRA contribution for a Backdoor Roth. The physician can't simply designate the new $7,500 as the only money being converted and treat the entire conversion as after-tax money. The existing pre-tax IRA balance affects the percentage of the conversion that is taxable under the pro-rata calculation. Using simplified numbers, only about 11% of a $67,500 combined IRA balance would represent the $7,500 of after-tax basis. A conversion of $7,500 could therefore be largely taxable rather than producing the clean Backdoor Roth result the physician expected.

A Solo 401(k) is different because assets held inside the qualified retirement plan aren't included as traditional IRA balances on Form 8606. That can make the Solo 401(k) significantly more attractive for a physician who expects to use a Backdoor Roth IRA year after year.

A Solo 401(k) May Also Help Clean Up Existing IRA Assets

The Backdoor Roth issue doesn't always begin with a SEP IRA – a physician may have a traditional rollover IRA from an old hospital 401(k), residency retirement plan, previous employer, or another job. Even if that account has nothing to do with current 1099 income, the pre-tax IRA balance can still affect the pro-rata calculation.

In some cases, a Solo 401(k) can provide another option. If the Solo 401(k) plan accepts incoming rollovers, eligible pre-tax IRA assets may potentially be rolled into the plan. Retirement plans aren't required to accept rollovers, so the physician needs to confirm what the specific Solo 401(k) document allows before moving anything.

When an appropriate rollover moves eligible pre-tax IRA money into a qualified plan, it can reduce or eliminate the pre-tax traditional IRA balance included in the Backdoor Roth calculation. For the right physician, that means the Solo 401(k) can solve two problems at once: creating a retirement home for current 1099 income while helping reorganize older retirement assets in a way that works better with the broader tax strategy.

That decision deserves careful review, particularly if an IRA contains after-tax basis or multiple types of retirement money.

When a SEP IRA Could Still Be Better for a Physician With 1099 Income

The Solo 401(k) has several advantages, but complexity has a cost, too; a SEP IRA is relatively straightforward to establish and administer, which can be appealing to a physician whose primary goal is simply to make an employer retirement contribution against self-employment income.

It may deserve consideration when:

• The physician has already used all employee elective-deferral capacity through a workplace retirement plan.

• Backdoor Roth IRA planning isn't a concern.

• There aren't pre-tax IRA balances that need to be reorganized.

• The simplicity of the account is more valuable than additional plan features.

• The physician's business structure or circumstances make the potential contribution amounts similar.

  
  

A Solo 401(k) comes with more responsibility – a one-participant 401(k) is still a 401(k), and IRS rules apply even though only the owner, or the owner and spouse, participate. Once plan assets exceed $250,000 at the end of the year, a one-participant plan will generally have an annual Form 5500-EZ filing requirement, and a final return is generally required when the plan is terminated.

That extra administration isn't necessarily a reason to avoid the account, but it should be part of the decision rather than discovered years later.

Employees Can Change the SEP IRA vs. Solo 401(k) Decision Entirely

Physicians building a larger side business need to consider one more question: Does anyone else work for the business?

A Solo 401(k) is designed for an owner with no common-law employees, or for the owner and the owner's spouse. Once eligible employees enter the picture, it may no longer function as a one-participant plan, and the compliance requirements can change substantially.

A SEP IRA can accommodate employees, but that doesn't necessarily make it inexpensive. Under many SEP arrangements, the employer generally has to contribute the same percentage of compensation for eligible employees that it contributes for the owner.

This can matter for a physician whose consulting or medical business is growing.

A retirement plan that works beautifully when the business consists of one physician and a laptop may need to be reconsidered once the practice begins adding staff.

SEP IRA vs. Solo 401(k) for Physicians: Which Is Better?

For many physicians with 1099 income, a Solo 401(k) deserves a close look because it can provide a combination of contribution flexibility, compatibility with Backdoor Roth IRA planning, and potential options for consolidating eligible pre-tax retirement assets.

A SEP IRA can still be an excellent account when simplicity is the priority and those additional features aren't needed. The harder cases are the physicians somewhere in between.

Perhaps you already max out a 403(b) at the hospital but earn another $60,000 from moonlighting. Maybe you opened a SEP IRA several years ago and have since started doing Backdoor Roth contributions. You could have an old rollover IRA, an S corporation, several sources of 1099 income, or a spouse participating in the business. You may simply be unsure how much you're actually allowed to contribute once everything is considered together.

Those are the situations where choosing an account based solely on which one has the highest advertised contribution limit can miss the larger opportunity. The better question is: How should your 1099 retirement plan fit with everything else you're already doing?

Put Your 1099 Income Into the Rest of Your Financial Plan

At YPP, we often see the SEP IRA vs. Solo 401(k) decision sitting in the middle of a much larger financial picture. A physician may already be contributing to a hospital 401(k) or 403(b), using a Backdoor Roth IRA, carrying retirement accounts from previous employers, making quarterly estimated tax payments on moonlighting income, or running that 1099 work through an S corporation. 

What looks like a simple question about where to make a retirement contribution can quickly become a question about taxes, retirement strategy, account structure, and how much of today's income needs to be saved in the first place. That's where having a financial planner and tax strategist who understands physicians can be especially valuable.

YPP provides physician-focused financial planning that looks at these decisions together rather than treating each account or tax question as a separate problem. We can help you evaluate how your W-2 and 1099 income interact, how much retirement contribution room you actually have, whether existing IRA balances complicate a Backdoor Roth strategy, and how a SEP IRA or Solo 401(k) fits alongside the rest of your investments, taxes, and long-term goals.

As a fiduciary financial planner, YPP's role is to help evaluate those choices based on what makes sense for your financial life, while our tax strategy work can help identify the tax consequences and planning opportunities created by 1099 income before they become year-end surprises. When coordination with a CPA, attorney, or other professional is needed, the goal is to keep those decisions connected rather than leaving you to piece the advice together yourself.

YPP is headquartered in Haddonfield and works with physicians and families throughout New Jersey, with deep roots in Palm Beach and communities across Florida, as well as clients in New York and Pennsylvania, including Philadelphia and the surrounding suburbs. We also provide fiduciary financial planning and tax strategy to physicians nationwide, so geography doesn't have to determine whether you can work with a planner who understands the financial decisions that come with a medical career.

The goal isn't simply to choose the retirement account with the most features or the largest contribution limit – it's to understand how that choice affects the rest of your plan.

If your 1099 income has created more questions around taxes, retirement contributions, Backdoor Roth planning, or how your side income should fit into your long-term goals, schedule a conversation with YPP. Our financial planning and tax strategy work can help you see what deserves attention now, what can wait, and how to make the different pieces of your financial life work together.

FAQs

Can a Physician Have a Solo 401(k) and a 403(b)?

Yes. A physician can potentially participate in a Solo 401(k) for eligible self-employment income while also participating in a 401(k) or 403(b) through an employer. However, the employee elective-deferral limit generally applies across the physician's plans rather than resetting for each one. Employer contribution limits have separate considerations, so the accounts should be reviewed together before determining how much to contribute.

Can a Physician Have a SEP IRA and a 401(k)?

Yes. Having access to a workplace 401(k) doesn't automatically prevent a physician from establishing a SEP IRA for a separate business with eligible self-employment income. Contribution limits and business ownership relationships can affect the calculation, so having both accounts doesn't necessarily mean the maximum can be contributed to each independently.

Does a SEP IRA Affect a Backdoor Roth IRA?

It can. SEP IRAs are included with traditional and SIMPLE IRAs when determining the taxable and nontaxable portions of certain Roth conversions on Form 8606. A substantial pre-tax SEP IRA balance can therefore cause part of a Backdoor Roth

conversion to be taxable under the pro-rata calculation.

Does a Solo 401(k) Affect a Backdoor Roth IRA?

Assets held inside a Solo 401(k) aren't included in the traditional IRA balance used on Form 8606 in the same way traditional, SEP, and SIMPLE IRA assets are. This is one reason physicians who regularly use the Backdoor Roth strategy may prefer a Solo 401(k).

Can I Roll an IRA Into a Solo 401(k)?

Potentially. A Solo 401(k) may accept certain eligible pre-tax retirement assets if the plan document permits incoming rollovers. Plans aren't required to accept them, so the account's specific rules should be reviewed before initiating a transfer.

How Much Can a Physician Contribute to a Solo 401(k) in 2026?

For 2026, the employee elective-deferral limit is $24,500, while the overall defined-contribution limit is $72,000 before applicable catch-up contributions. The physician's actual allowable contribution depends on compensation, business structure, other retirement-plan contributions, and whether the employee deferral has already been used through another employer plan.

Is a SEP IRA or Solo 401(k) Better for Moonlighting Income?

A Solo 401(k) often provides more flexibility when a physician has unused employee-deferral capacity or wants to preserve a clean Backdoor Roth strategy. A SEP IRA may be attractive when simplicity is more important and the physician doesn't need those additional features. The better choice depends on the physician's other retirement plans, IRA balances, business structure, income, and long-term tax strategy.