SEP IRA: Tax Deduction Guide for Self-Employed & Small Business Owners
A SEP IRA is a Simplified Employee Pension, established under IRC §408(k), that lets a self-employed person or small business owner make a large, fully deductible retirement contribution with almost no plan administration. It is employer-funded only: unlike a SIMPLE IRA or a 401(k), there is no employee salary-deferral feature. The business (or the sole proprietor, acting as employer) contributes to a traditional IRA set up for each eligible employee, including the owner. For a solo consultant, freelancer, or single-owner S-corp with strong income and no staff, it is often the fastest deduction to set up and the easiest to administer of any retirement plan option.
The tradeoff for that simplicity is the coverage rule: if you have eligible employees, you generally must contribute the same percentage of compensation for them that you contribute for yourself. That single rule is what makes a SEP IRA excellent for a one-person business and often wrong for one with staff.
2025 SEP IRA Contribution Limits
For the 2025 tax year, a SEP IRA contribution is limited to the lesser of 25% of compensation or $70,000, under the IRC §415(c) defined contribution limit. This is a per-participant cap, not a per-plan cap: each eligible employee's contribution is separately limited to 25% of that employee's compensation, capped at the dollar limit. There is no separate catch-up contribution for participants age 50 and older under a SEP IRA, which is one of the plan's real limitations compared to a 401(k).
2026 SEP IRA contribution limits are UNVERIFIED as of this writing. The IRS typically releases the following year's qualified-plan limits in the fall (historically late October or November) via a Revenue Procedure. Confirm the 2026 dollar limit against the published IRS figures before relying on it for 2026 planning; do not assume it simply repeats the $70,000 2025 figure.
The Self-Employed Contribution Calculation
For a common-law employee, the 25%-of-compensation limit is straightforward: 25% of W-2 wages. For a self-employed individual, sole proprietor, or partner, the calculation is more involved, and getting it wrong is the single most common SEP IRA mistake we see.
A self-employed person cannot simply take 25% of net Schedule C profit. The contribution must be calculated as 25% of net self-employment earnings after two reductions: (1) the deduction for one-half of self-employment tax, and (2) the SEP contribution itself. Because the contribution reduces the base it is calculated from, this circular calculation nets out to an effective rate of roughly 20% of net self-employment earnings before those reductions, not the full 25% a W-2 employee comparison would suggest.
IRS Publication 560 contains the required worksheet for this calculation (the "Deduction Worksheet for Self-Employed" in the SEP chapter). We run this worksheet for every self-employed SEP client rather than approximating, because the difference between the naive 25% figure and the correct effective rate is material at higher income levels and an over-contribution creates excise tax exposure under IRC §4973.
Where the Deduction Goes on Your Return
Schedule C Sole Proprietors
A sole proprietor's SEP IRA contribution is not deducted on Schedule C. It is an above-the-line adjustment to income, reported on Schedule 1, Line 16 ("Self-employed SEP, SIMPLE, and qualified plans"), and it flows to Form 1040. This matters because Schedule C net profit still drives self-employment tax under Schedule SE; the SEP deduction reduces income tax but does not reduce SE tax.
S-Corporation and Partnership Owners
For an S-corporation, the SEP contribution on behalf of an owner-employee is a deductible business expense at the entity level, and it must be based on the owner-employee's W-2 wages from the S-corp, not on the entity's overall net income or K-1 distributions. Reasonable-compensation exposure applies here just as it does elsewhere in S-corp payroll planning: the SEP contribution amount is only as large as the W-2 wage base supports.
For a partnership, an owner's SEP contribution is based on the partner's net earnings from self-employment as reported on Schedule K-1, using the same reduced-base calculation described above (after one-half SE tax and the contribution itself), not the partnership's gross allocation.
The Deadline Advantage
The single biggest structural advantage a SEP IRA has over a Solo 401(k) is timing. A SEP IRA can be established and funded as late as the extended due date of the business's tax return, including extensions. For a Schedule C sole proprietor, that means the SEP can be opened and funded as late as October 15 of the following year if the return is on extension. For a calendar-year S-corporation, the extended deadline is generally September 15.
A Solo 401(k), by contrast, must be established (the plan itself opened) by December 31 of the tax year, even though certain contributions can still be made after year-end. If you are reviewing your tax situation in March or April and realize you want a large retirement deduction for the prior year, a SEP IRA may still be available; a Solo 401(k) for that year generally is not, because the plan document deadline has already passed.
The Coverage Rule: Why a SEP Often Breaks Down With Employees
A SEP IRA is not selective. If you have eligible employees, you must contribute the same percentage of compensation for each of them that you contribute for yourself. Under the standard SEP eligibility rules, an employee is eligible if they are age 21 or older, have worked for the employer in at least 3 of the last 5 years, and received at least $750 in compensation for 2025 (this compensation threshold is also subject to annual IRS adjustment; confirm the current-year figure before applying it).
This is where a SEP IRA frequently stops making sense. A solo consultant who contributes 25% of their own compensation and then hires a full-time employee must generally contribute the same 25% for that employee, on top of wages. For many small businesses, that cost eliminates the SEP as a viable plan the moment the first eligible employee comes on board, and pushes the analysis toward a 401(k) with different eligibility and vesting design options instead.
SEP IRA vs. Solo 401(k)
For a self-employed individual or single-owner business with no other eligible employees, the SEP IRA and the Solo 401(k) are the two plans most worth comparing. Neither is universally better; the right choice depends on income level, whether you want Roth contributions, whether you might want a plan loan, and how far past year-end you are when you decide to act.
| Feature | SEP IRA | Solo 401(k) |
|---|---|---|
| Contribution structure | Employer contribution only, up to the lesser of 25% of compensation or $70,000 (2025) | Employee salary deferral (up to $23,500 for 2025, plus $7,500 catch-up for age 50+) PLUS employer profit-sharing contribution (up to 25% of compensation) — combined room is generally higher for the same income level |
| Roth option | No | Yes, Roth solo 401(k) deferrals are available |
| Plan loans | Not permitted | Permitted if the plan document allows it |
| Establishment deadline | Extended due date of the business return (e.g. Oct 15 for Schedule C on extension) | Must be established by Dec 31 of the tax year |
| Administration | Minimal; no Form 5500 filing requirement | Simple while balance is under $250,000 (no Form 5500); Form 5500-EZ required once plan assets exceed $250,000 |
| Best fit | Late deciders, simplest possible administration, no interest in Roth or loans | Higher contribution room at moderate income, wants Roth deferrals or loan access, can commit before Dec 31 |
Because the Solo 401(k) allows both an employee deferral and an employer profit-sharing contribution, it typically produces more total contribution room than a SEP IRA at moderate self-employment income levels, since the SEP relies on the 25%-of-adjusted-earnings calculation alone. At very high income, both plans tend to converge toward the same overall §415(c) dollar limit. We model both sides of this comparison for every new self-employed retirement plan engagement, because the better plan for a given client depends on their specific income and timing, not a general rule of thumb.
Common SEP IRA Mistakes
- Using 25% of gross Schedule C profit instead of the reduced self-employment earnings figure. This overstates the allowable contribution and creates an excess-contribution problem that has to be corrected, often with an excise tax under IRC §4973 if not fixed in time.
- Missing the extended-due-date deadline because the return was filed on time without an extension in place. The SEP deadline tracks the tax return's actual due date, including extensions, but only if the extension was properly filed. A client who files on time in April without extending cannot fund a SEP for that year past April.
- Hiring the first employee and not revisiting the coverage rule. A SEP that worked cleanly for a solo owner can become expensive or impractical the moment an eligible employee is added, and the contribution obligation to that employee is not optional once eligibility is met.
- Basing an S-corp owner's contribution on K-1 income or distributions instead of W-2 wages. Only W-2 compensation counts for an S-corp owner-employee's SEP calculation.
- Assuming the SEP deduction reduces self-employment tax. It does not. The SEP deduction is an income tax adjustment on Schedule 1; SE tax is calculated on Schedule SE from net Schedule C profit before the SEP deduction is applied.
How Silicon Valley Tax Approaches SEP IRA Planning
A SEP IRA engagement with our team starts with the Publication 560 worksheet calculation run against your actual projected net self-employment earnings, not an estimate, so the contribution figure we give you is the one you can actually fund. If you have or are considering hiring employees, we run the coverage-rule cost comparison before you commit, and we compare the SEP against a Solo 401(k) side by side when your income and timing make that comparison worth having. Our broader retirement tax planning practice handles SEP, Solo 401(k), traditional and Roth IRA, and defined benefit plan design together, and our small business CPA services coordinate the entity-level and payroll mechanics that feed the S-corp and partnership calculations above.
FAQ: SEP IRA Tax Deduction
What is the SEP IRA contribution limit for 2025?
For 2025, a SEP IRA contribution is limited to the lesser of 25% of compensation or $70,000 per participant, under IRC §415(c). For a self-employed individual, that 25% is applied to net self-employment earnings after deducting one-half of self-employment tax and the SEP contribution itself, which works out to roughly 20% of net earnings before those reductions. 2026 limits are not yet confirmed; check the current IRS-published figures before relying on a number for the 2026 tax year.
How do I calculate my SEP IRA contribution if I'm self-employed?
You cannot take 25% of your net Schedule C profit directly. IRS Publication 560 provides the required worksheet, which reduces your net self-employment earnings by one-half of your self-employment tax deduction and by the SEP contribution amount itself before applying the 25% rate. The result is an effective contribution rate close to 20% of your pre-adjustment net earnings, not 25%. S-corp owners use W-2 wages instead, and partners use Schedule K-1 net earnings from self-employment with the same reduced-base approach.
When is the SEP IRA contribution deadline?
A SEP IRA can be established and funded as late as the extended due date of the business's tax return, including extensions. For a Schedule C sole proprietor on extension, that is generally October 15 of the following year. For a calendar-year S-corporation on extension, that is generally September 15. This is later than the deadline for a Solo 401(k), which must be established by December 31 of the tax year even though some contributions can be made afterward.
Can I have a SEP IRA if I have employees?
Yes, but the coverage rule means you generally must contribute the same percentage of compensation for every eligible employee that you contribute for yourself. An employee is typically eligible if they are age 21 or older, have worked for you in at least 3 of the last 5 years, and met the annual compensation threshold ($750 for 2025, subject to IRS adjustment). This rule is what often makes a SEP impractical once a business hires its first eligible employee, and it should be modeled against the cost of alternative plans before adopting a SEP with staff already on payroll.
Is a SEP IRA or a Solo 401(k) better for a self-employed person?
It depends on income, timing, and features you want. A Solo 401(k) allows both an employee salary deferral (up to $23,500 for 2025, plus a $7,500 catch-up for age 50 and older) and an employer profit-sharing contribution, which typically produces more total contribution room at moderate income levels than a SEP's employer-only 25% calculation. A Solo 401(k) also allows Roth deferrals and plan loans, which a SEP does not. A SEP IRA's advantage is administrative simplicity and, critically, a much later establishment deadline: a Solo 401(k) must be opened by December 31 of the tax year, while a SEP can be opened as late as the extended filing deadline of the following year. If you are deciding after year-end, the SEP is often the only option still available.
Does the SEP IRA deduction reduce my self-employment tax?
No. The SEP contribution is an above-the-line income tax deduction reported on Schedule 1, Line 16, not a Schedule C business expense. Self-employment tax on Schedule SE is calculated from your net Schedule C profit before the SEP deduction is applied, so the SEP contribution lowers your income tax but has no effect on your self-employment tax liability.
Talk to Us Before You Fund Your SEP
A SEP IRA can produce a large, legitimate deduction with minimal paperwork, but the calculation, the deadline, and the coverage rule all have to be right before you fund it. Our team includes CPAs and EAs helping self-employed clients and small business owners across the Bay Area run the Publication 560 worksheet correctly, compare SEP against Solo 401(k) where it matters, and file the deduction where it actually belongs on the return. Schedule a complimentary consultation or call us at (408) 383-9870 before your next contribution or extension deadline.