Retirement and Tax Strategy
SEP IRA Contribution Limits 2026: How Business Owners Compare a SEP to a Solo 401(k) Before Year-End
The SEP IRA contribution limits for 2026 are only part of the decision. This guide compares a SEP with a Solo 401(k) and a traditional 401(k), walks through the deadlines that actually fall on December 31, and covers the Pennsylvania rules that change the after-tax math.
By Jonathan Dane, CFA, CFP® · Updated October 2026
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What Is the Maximum 2026 SEP IRA Contribution Limit?
The 2026 SEP IRA contribution limit is the lesser of 25% of compensation or $72,000, with a compensation cap of $360,000. For sole proprietors and partners, the effective rate is 20% of net self-employment earnings after deducting half of self-employment tax. Below the Social Security wage base, that works out to roughly 18.6% of Schedule C net profit.
Two separate adjustments produce that result. The 25% rate is converted to 20% because the contribution itself reduces the earnings it is based on (25% divided by 1.25). Separately, half of your self-employment tax is subtracted from net profit before that 20% is applied.
Sources: IRS Notice 2025-67, IRS COLA Adjustments Table, and IRS Publication 560. As of October 2026.
Plan Comparison
SEP IRA vs. Solo 401(k) vs. Traditional 401(k) in 2026
A side-by-side look at the three most common small business retirement plans for the 2026 tax year, for owners with and without employees.
| Feature / Rule | SEP IRA | Solo 401(k) | Traditional 401(k) |
|---|---|---|---|
| Who Can Use It | Any business, with or without employees | Only businesses with no employees other than the owner and spouse | Any business; nondiscrimination testing applies |
| Employee Deferral Limit | Not permitted (employer contributions only) | $24,500 | $24,500 |
| Employer Contribution | Up to 25% of compensation (20% of adjusted net SE earnings for sole proprietors) | Up to 25% of compensation (20% of adjusted net SE earnings for sole proprietors), subject to the total limit | Per plan formula, subject to the total limit |
| Total Annual Additions Limit | $72,000 | $72,000, excluding catch-ups | $72,000, excluding catch-ups |
| Catch-Up (Age 50+) | Not permitted | $8,000, or $11,250 for ages 60 to 63 | $8,000, or $11,250 for ages 60 to 63 |
| Employee Deferral Deadline | Not applicable | Existing plan: election by Dec 31, 2026 (S-corp owners must run deferrals through payroll by Dec 31). New plan: under SECURE 2.0, a sole proprietor may make first-year deferrals if the plan is opened by the unextended return due date. | Through payroll by Dec 31, 2026 |
| Employer Contribution Deadline | Plan can be opened and funded by the filing deadline including extensions: Oct 15, 2027 for individual filers; Sept 15, 2027 for S-corps and partnerships | Filing deadline including extensions | Filing deadline including extensions |
| Annual Filing | No Form 5500 | Form 5500-EZ only once plan assets exceed $250,000 (and in the final plan year) | Form 5500 annually |
| Backdoor Roth Compatibility | Pre-tax SEP balances count in the IRA pro-rata calculation* | Plan balances are excluded from the pro-rata calculation | Plan balances are excluded from the pro-rata calculation |
*SECURE 2.0 permits Roth employer contributions to a SEP where the custodian supports it. Roth SEP dollars are taxed in the year contributed and do not add to the pre-tax balance used in the pro-rata calculation.
Mandatory Roth catch-up: beginning in 2026, if your 2025 FICA wages from the plan sponsor exceeded $150,000, catch-up contributions to a 401(k) must be made as Roth. Sole proprietors with only Schedule C income have no FICA wages and are not affected.
Sources: IRS Notice 2025-67, IRS One-Participant 401(k) Plans, IRS Form 5500-EZ, IRS Catch-Up Contributions. As of October 2026. Limits are per individual; special earned income calculations apply to sole proprietors.
Strategic Choice
Understanding the Core Differences and Trade-Offs
A SEP IRA is funded entirely by employer contributions, with no employee deferrals. That keeps administration simple, but it means the contribution depends entirely on your compensation or net earnings for the year.
A Solo 401(k) lets you contribute as both employee and employer, which often reaches the $72,000 limit at a lower income. It is available only if the business has no employees other than you and your spouse.
How much income it takes to max out a SEP at $72,000 depends on how you are taxed:
- S-corp owners (W-2 wages): $288,000 of W-2 salary, since 25% of $288,000 is $72,000.
- Sole proprietors: $360,000 of net earnings after the half-SE-tax deduction, which is roughly $376,000 of Schedule C net profit using the 2026 Social Security wage base of $184,500.
With a Solo 401(k), the $24,500 employee deferral plus an employer profit-sharing contribution can reach the same $72,000 total on meaningfully less income. Higher contributions also mean more pre-tax money that will be taxed on withdrawal, so the right amount depends on your current and expected future tax rates. Our Solo 401(k) contribution limits guide covers the calculation in detail.
Source: SSA Contribution and Benefit Base. Figures are estimates; the Additional Medicare Tax is not deductible and is excluded.
Pros and Cons at a Glance
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1
SEP IRA simplicity: Easy to open, no Form 5500, and can be established and funded up to the extended filing deadline. The trade-off is no deferrals, no catch-ups, and a lower contribution at moderate income levels.
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2
Solo 401(k) flexibility: Deferrals, catch-ups of $8,000 (or $11,250 at ages 60 to 63), and Roth options. The trade-off is more paperwork, including Form 5500-EZ once assets exceed $250,000, and a Dec 31 deferral election in existing plans.
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3
Hiring changes the comparison: Once you have an eligible non-spouse employee, a Solo 401(k) is no longer available and you would move to a standard 401(k) with testing, or a SEP. Under a SEP, you must contribute the same percentage of pay for every eligible employee as you do for yourself.
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4
Roth catch-up for S-corp owners: If your 2025 W-2 wages from your S-corp exceeded $150,000, any 2026 401(k) catch-ups must be made as Roth. If the plan doesn't offer Roth, you lose the catch-up. See our 2026 401(k) limits guide.
Tax Pitfall
The SEP IRA Pro-Rata Trap for Backdoor Roth Contributions
Many business owners use the backdoor Roth to build Roth assets when their income exceeds the direct contribution limits. A pre-tax SEP IRA balance can make most of that conversion taxable.
How the Pro-Rata Rule Operates
The IRS combines all traditional, SEP, and SIMPLE IRA balances to determine how much of a Roth conversion is taxable. You cannot choose to convert only your nondeductible contributions.
Suppose you have a $92,500 SEP IRA and make a $7,500 nondeductible traditional IRA contribution, the 2026 limit. Your total IRA balance is $100,000. Converting the $7,500 makes 92.5%, or about $6,938, taxable as ordinary income.
The measurement date is December 31. The calculation on Form 8606 uses your IRA balances on December 31 of the conversion year, not on the day you convert.
The Solo 401(k) Roll-In and Its Year-End Deadline
Employer plan balances are excluded from the pro-rata calculation. If you roll pre-tax SEP assets into a Solo 401(k), your December 31 IRA balance may drop to zero, which can let a backdoor Roth convert with little or no tax.
Two conditions apply. The rollover must be completed by December 31 of the conversion year, and the receiving plan document must accept roll-ins. Not every Solo 401(k) provider does, so confirm before you start.
Rolling assets into a 401(k) can also change investment options, fees, and creditor protection. Weigh those trade-offs before moving the money.
Roth SEP contributions, where available, are not pre-tax and do not add to the pro-rata balance. Sources: IRS Form 8606, IRS IRA Contribution Limits. As of October 2026.
Pennsylvania Tax Strategy
How Pennsylvania Treats Owner Retirement Contributions
Pennsylvania Personal Income Tax follows its own rules. SEP and Solo 401(k) contributions are deductible on your federal return, but sole proprietors and partners generally cannot deduct contributions for themselves against Pennsylvania taxable income. Those dollars remain subject to Pennsylvania's flat 3.07% rate in the year you contribute.
The other half of the picture matters just as much. Pennsylvania generally excludes distributions from employer retirement plans after retirement and from IRAs, including SEPs, after age 59½. That exclusion applies whether or not the contributions were taxed going in. For owners, the net effect is that contributions are generally taxed by Pennsylvania going in and generally not coming out, the reverse of the federal treatment.
Contributions you make for common-law employees remain deductible business expenses for Pennsylvania purposes. S-corp shareholder-employees are treated differently from sole proprietors and partners, so confirm your situation with your CPA before relying on either result.
Source: Pennsylvania Department of Revenue Personal Income Tax Guide. As of October 2026.
Pennsylvania PIT Retirement Rules for Owners
Owner Contributions Are Not Deductible
For sole proprietors and partners, contributions to your own SEP or Solo 401(k) do not reduce Pennsylvania taxable income.
Qualifying Distributions Are Generally Not Taxed
Pennsylvania generally excludes employer plan distributions after retirement and IRA distributions, including SEPs, after age 59½. The exclusion does not depend on whether the contributions were taxed going in.
Contributions for Your Employees Are Deductible
Employer contributions on behalf of common-law employees are deductible business expenses for Pennsylvania net profits.
Employee Deferrals Are Included in PA Compensation
401(k) salary deferrals are included in Pennsylvania taxable compensation when contributed.
Frequently Asked Questions
Common Questions About SEP IRA Rules in 2026
Is the self-employed SEP contribution limit 20% or 25%?
For sole proprietors and partners, the limit is effectively 20% of net self-employment earnings after deducting half of self-employment tax. The plan rate is 25%, but because the contribution reduces the earnings it is calculated on, 25% divided by 1.25 gives 20%. The half-SE-tax deduction is a separate reduction to the base. Combined, the contribution is roughly 18.6% of Schedule C net profit for income below the Social Security wage base.
What is the 3-of-5 employee eligibility rule for a SEP IRA?
A SEP may require employees to be at least 21, to have worked for the business in at least 3 of the last 5 years, and to have received at least $800 in compensation in 2026, per IRS Notice 2025-67. Any service in a year counts toward the three years, even a few weeks of part-time or seasonal work. Once an employee qualifies, you must contribute the same percentage of pay for them as for yourself.
How do SEP IRA contribution rules apply to LLC owners?
It depends on how the LLC is taxed. If it is taxed as a sole proprietorship, contributions are based on net self-employment earnings using the adjusted 20% calculation, and the SEP can be funded until Oct 15, 2027 with an extension. If it is taxed as a partnership, partners use the same adjusted 20% calculation, but the entity deadline applies: Sept 15, 2027 with an extension. If it is taxed as an S-corp, contributions are based on W-2 wages at up to 25%, capped at $72,000, and the same Sept 15, 2027 entity deadline applies with an extension.
Can I max out an employer-sponsored 401(k) and a SEP IRA in the same year?
Generally yes, if your side business is not under common control with your employer. Your $24,500 deferral limit is shared across every 401(k) you participate in. Employer contributions from your side business to a SEP are subject to their own $72,000 limit, separate from your day job's plan.
Is there an age limit for contributing to a SEP IRA?
No. As long as you have qualifying earned income, you can contribute at any age. RMDs still apply once you reach the required age: 73 if you were born from 1951 through 1959, and 75 if you were born in 1960 or later. See our 2026 RMD rules guide.
Which retirement plan deadlines actually fall on December 31?
A SEP can be opened and funded after year-end. These items cannot wait: Solo 401(k) deferral elections in an existing plan, S-corp owner deferrals run through payroll, and any SEP-to-401(k) roll-in meant to clear your IRA balance before a backdoor Roth. A brand-new Solo 401(k) can still accept a sole proprietor's first-year deferrals if it is opened by the unextended return due date.
Independent Wealth Advisory
Integrate Your Retirement and Tax Strategies with Fiduciary Guidance
At Defiant Capital Group, we treat retirement plan selection as part of your overall tax and wealth plan. We help business owners and founders coordinate plan design, entity structure, Roth strategy, and year-end deadlines, working alongside your CPA. Compare this guide with our Solo 401(k) limits and 401(k) limits guides.
From our office at 50 Pennwood Place in Warrendale, we serve clients in Wexford, Pittsburgh, and across the country. Every retirement and tax strategy involves trade-offs, and results depend on individual circumstances.
Defiant Capital Group
An independent, fiduciary RIA led by Jonathan Dane, CFA, CFP®.
Office:
50 Pennwood Place, Warrendale, PA 15086
Serving Warrendale, Wexford, and Pittsburgh
Phone:
412-697-1435
Email:
defiant@defiantcap.com