Self-employed

Solo 401(k) for Self-Employed Workers: Structure, Contributions, and Deadlines (High Level)

A solo 401(k)—often called a one-participant 401(k)—lets self-employed individuals wear both “employee” and “employer” hats for contribution purposes, subject to IRS limits and net earnings from self-employment. This article is an orientation for solo 401k calculator and self employed 401k calculator searches; our site’s main 401k calculator models W-2 style salary patterns, so adjust assumptions if you use it for rough exploration.

Who Typically Qualifies

Generally a business with no eligible employees other than the owner (and possibly a spouse per plan rules). Hiring employees can disqualify solo 401(k) status—get legal/plan advice before hiring.

Two Buckets: Elective Deferrals and Employer Nonelective / Profit-Sharing

Employee elective deferrals

Subject to the same annual deferral limits as other 401(k) plans (verify each year on IRS.gov).

Employer profit-sharing

Computed from net earnings using IRS rules for self-employment—this is where solo plans differ sharply from simple salary multiplication.

Solo 401(k) vs. SEP IRA (Plain-Language Contrast)

SEP contributions are employer-only; solo 401(k) can combine deferrals plus profit-sharing, often allowing higher retirement savings for a given income—again, run numbers with a tax pro.

For sponsor-level comparisons of SEP/SIMPLE vs. a full 401(k)—adjacent self-employment searches—see SEP vs. SIMPLE vs. 401(k).

Establishment and Funding Deadlines

Deadlines depend on tax year, entity type, and plan adoption—do not rely on a blog for compliance dates.

Form 1099-NEC vs. W-2, Schedule C, and S-corp wages

How self-employment earnings are measured

Solo 401(k) employer contributions use net earnings from self-employment after certain deductions—different from gross 1099 revenue. S-corporation owners who take W-2 wages use a hybrid structure; only wages may count for deferrals in some designs—your CPA must map the right compensation definition.

Multiple businesses

Controlled group rules may aggregate businesses for plan purposes—opening a second solo plan without analysis can create disqualification risk.

Common misconceptions

“Solo means I can skip Form 5500 forever”

Filing thresholds exist, but asset levels and plan design can trigger reporting—your CPA should map Form 5500-EZ or full filing requirements annually.

“I can max employee deferrals on gross 1099 revenue”

Employer contributions use net earnings from self-employment after deductions—gross invoices overstate what the IRS math allows.

“Hiring one part-time helper won’t affect my solo plan”

Eligibility, controlled groups, and leased employees can terminate solo status—get a determination before adding payroll.

FAQ

Can I have a solo 401(k) and a day job 401(k)?

Yes, but individual elective deferral limits apply across all plans—coordinate contributions to avoid excess deferrals.

Is a solo 401(k) cheaper than SEP?

Filing Form 5500-EZ may be required once assets exceed thresholds—compare total compliance cost with SEP simplicity.

Can I take a loan from my solo 401(k)?

Only if the plan document permits loans and you follow repayment rules—setup documents must explicitly allow them.

Checklist: solo 401(k) housekeeping

Confirm only the owner (and spouse if applicable) is eligible—document hiring plans annually.
Track elective deferrals across all 401(k) plans if you also have a day-job plan.
Reconcile profit-sharing calculations with Schedule SE / corporate wage statements.
Calendar plan adoption, funding, and any Form 5500 deadlines with your CPA.