Solo 401(k)
401(k) retirement plan covering only a self-employed business owner and optionally their spouse.
Definition
A Solo 401(k), also called Individual 401(k), Self-Employed 401(k), or Uni-K, is a qualified retirement plan adopted by an unincorporated sole proprietor, single-member LLC, S-corp owner, or partnership where the only employees are the owner(s) and their spouse(s). It allows both employee deferral (up to $23,500 in 2025, $31,000 if age 50+) and employer profit-sharing contribution (up to 25% of compensation).
Why it matters
For IRS Form 5500-EZ, this term helps decide which records, dates, values, or review questions belong in the packet.
How the tool uses it
Solo 5500 treats this as a review signal. The user enters the facts, checks the source-linked explanation, reviews the packet, and files through the official channel when the supported case still fits.
When to check the source
Check the official source when the answer depends on eligibility, late filing relief, official correspondence, valuation, or a fact you cannot verify from your own records.
Source and review date
Last reviewed: . Use the linked source for the official wording behind this term.
Official source: IRS Form 5500-EZ filing notices