Solo 401(k)
Category: Retirement & health
A 401(k) for a business with no employees other than a spouse, combining employee elective deferrals and employer profit-sharing in one plan.
How Solo 401(k) fits 2026 planning
Solo 401(k) sits inside retirement contribution limits, distribution timing, and how pre-tax vs Roth choices change AGI. For tax year 2026, US Tax Tools treats year-scoped constants (brackets, contribution limits, wage bases, credit schedules) as separate datasets — so explanations of Solo 401(k) should be read with the same year selected in any linked calculator.
Category focus: Retirement & health. Readers usually land on this page while comparing a paycheck estimate, a credit phaseout, or a retirement contribution room figure that depends on understanding Solo 401(k) first.
Worked example
In 2026 an under-50 owner can combine up to $24,500 of deferrals with an employer contribution subject to compensation and §415 limits.
Treat the example as a teaching sketch, not a filing position. Change filing status, state residency, or mid-year events and the same definition of Solo 401(k) can produce a different cash outcome even when the glossary text stays the same.
What to watch for
Definitions of Solo 401(k) can differ slightly across IRS publications, SSA rules, Marketplace subsidy worksheets, and state agencies. When two programs both say “income,” confirm which modification rules apply — MAGI for one credit is not always MAGI for another.
Legislation and inflation adjustments can move the dollar thresholds around Solo 401(k) without renaming the concept. Prefer the effective date on the primary source (Rev. Proc., SSA notice, USDA table, or state DOR bulletin) over any blog summary — including this one if a later notice supersedes it.
Confirm how Solo 401(k) appears on your forms by reading the IRS instructions for the schedules that match your facts. Educational definitions here cannot capture every exception or state overlay.
Next step
When you are ready to model numbers, open the Solo 401(k) related calculator on US Tax Tools. Engines keep tax-year datasets separate so a 2025 habit does not silently reuse a 2026 constant.
Related reading: Tax insights for longer 2026 explainers, Methodology for how engines store cents and traces, and Disclaimer for educational-use limits.