If you run your own business and contribute to a SEP IRA, SIMPLE IRA, or solo 401(k), there’s a good chance you have mishandled the deduction; not by missing it, but by reporting it in the wrong place on your return.

It’s one of the most common errors among self-employed taxpayers, and it’s easy to understand why: you own the business. The money came out of your business account. Naturally, you assume the deduction belongs on Schedule C, with business expenses.

But, it usually doesn’t. And where a deduction lands on your return isn’t just an accounting formality. It can affect how much tax you owe, distort other calculations, and in some cases, cause you to leave money on the table.

Here’s what you need to know.

The basic rule and why it exists

If you are a sole proprietor (or a single-member LLC treated as a sole proprietor for tax purposes), contributions you make to a retirement plan for yourself are generally deducted on Schedule 1 of Form 1040, not on Schedule C.

Contributions made for your employees are a different story. Those generally belong on Schedule C as an ordinary business expense.

The owner-versus-employee distinction is the entire issue. As a self-employed owner, your retirement contribution isn’t calculated like a regular business expense. It’s determined under a special formula tied to your net earnings from self-employment (earnings that must first be adjusted for the self-employment tax deduction before the retirement contribution calculation can even begin). Because the deduction is computed under a separate set of rules, the IRS treats it separately. It belongs on the individual side of your return, not embedded in the business profit calculation.

What happens when you get it wrong

Deducting your own contribution on Schedule C instead of Schedule 1 isn’t just a technical error; it creates a cascade of downstream problems.

Consider a simple example. Say you have $100,000 in net Schedule C profit and make a $20,000 retirement contribution for yourself.

If the deduction is incorrectly placed on Schedule C:

• Reported Schedule C profit: $80,000
• Self-employment tax is computed on $80,000 (understated)
• The SE tax deduction is too small
• The allowable retirement contribution itself may be miscalculated, since the formula depends on correctly stated SE earnings

If reported correctly on Schedule 1:

• Schedule C profit: $100,000 
• SE tax is computed on the full $100,000
• SE tax deduction is taken on Schedule 1
• The retirement deduction is then calculated correctly and also taken on Schedule 1

Misplacing the deduction doesn’t just move a number; it corrupts the sequence of calculations that flow from it. When preparers catch this, the fix typically requires unwinding several connected figures.

Does this apply to you? It depends on your entity

These rules generally apply to sole proprietors, single-member LLCs disregarded for federal tax purposes, and partners in a partnership. For partners, the same logic holds: the partnership can deduct contributions made for common-law employees on the partnership return, but each partner’s own retirement contribution is deducted on the partner’s individual return through Schedule 1.

S corporation shareholders are a meaningful exception. An S corp shareholder-employee is treated as an employee of the corporation, receiving W-2 wages. Retirement plan contributions (both the elective deferral and any employer match) are generally handled at the entity level on Form 1120-S, not through the shareholder’s individual Schedule 1. The planning dynamics, tax treatment, and reporting mechanics are all materially different for S corp owners, and that distinction often factors into the entity selection conversation.

If you operate as an S corp or are weighing whether to make that election, the retirement contribution treatment is one of several factors worth analyzing carefully.

A note on SIMPLE IRAs

SIMPLE IRAs sit in an interesting position. If you have employees, their SIMPLE contributions, including any matching contributions you make as the employer, are generally deductible as business expenses. Your own contributions as the self-employed owner are handled separately, through the self-employed retirement deduction rules.

So within a single plan, contributions can flow to different parts of the return depending on who they’re for. 

The Solo 401(k) question: when you’re both employer and employee

Solo 401(k) plans create another layer of confusion (and a genuine planning opportunity) because they use terminology borrowed from traditional employer plans: employee elective deferral and employer profit-sharing contribution. As a self-employed individual, you’re technically filling both roles.

Here’s the important clarification: for a sole proprietor, both components are still deducted on Schedule 1. The plan’s internal labeling doesn’t change where the deduction lands on your tax return. What it does change is how much you can potentially contribute.

This is where structure matters for planning purposes. Compare two self-employed individuals, each with $100,000 in net Schedule C profit in 2026:

SEP IRA contributor: The SEP contribution is limited to roughly 25%  of net self-employment earnings after the SE tax deduction (approximately $23,200 in this scenario).

Solo 401(k) contributor:

• Employee elective deferral: up to $24,500 (up to $32,000 if age 50-59 or 64+; up to $35.750 if age 60-63).
• Employer profit-sharing contribution: approximately $23,200 (up to 25% of net earnings) Total limit lesser of 100% of compensation or $72,000 ($80,000 if 50-59 or 64+; $83,250 if 60-63)
• Combined total: approximately $47,700 (if under age 50)

Same income. Same tax situation. Roughly twice the deduction and tax-sheltered growth, simply by choosing the right plan.

The gap narrows at higher income levels, and at very high incomes the two plans approach the same ceiling (the 2026 IRC §415 limit is $72,000, or $80,000/$83,250 for those in the applicable catch-up ranges). But for self-employed individuals with moderate incomes who want to maximize contributions, the solo 401(k)’s ability to stack an employee deferral on top of the employer contribution can be a meaningful advantage.

The Schedule 1 placement is actually a feature, not a consolation

Here’s a framing shift worth making: the fact that your retirement deduction lands on Schedule 1 rather than Schedule C isn’t a quirk to work around. In some respects, it’s advantageous.

Schedule 1 deductions reduce your AGI and AGI is the input for a number of other calculations that Schedule C profit, on its own, doesn’t directly affect. A lower AGI can:

• Help you stay below IRMAA thresholds that trigger Medicare premium surcharges (2026 initial threshold $109,000 single/$218,000 MFJ)
• Reduce exposure to the 3.8% net investment income tax, which applies above $200,000 single/$250,000 MFJ
• Keep you within the QBI deduction range before phase-outs begin (2026 thresholds, $197,300 single/$394,600 MFJ) 

When retirement contributions are large enough to meaningfully affect AGI, these secondary benefits can be worth more than the straightforward income tax savings on the contribution itself. That’s not a reason to over-contribute, but it is a reason to think holistically about how the deduction interacts with the rest of your return.

The right reporting does more work than most people realize

The mechanics aren’t necessarily complicated once you understand the logic, but they’re easy to get wrong.

If you’re not certain where your retirement contributions are landing, or whether you’re in the right plan to begin with, it’s worth a conversation with your CPA before the next filing season arrives. 

For more personalized guidance, please contact our office.