The Solo 401k for the Self-Employed, Explained: What One-Person Businesses Can Do That Nothing Else Allows
Sam's List Editorial | 2026-06-23
The Solo 401k for the Self-Employed, Explained: What One-Person Businesses Can Do That Nothing Else Allows If you run a one-person business, you have a retirement account most employees would kill for. Almost nobody uses it right. Here is the Solo 401k self-employed explained in one line: it lets you contribute to your own retirement plan as both the employee and the employer. That double role is the whole game. It is also the thing a SEP IRA and a regular IRA structurally cannot do. The result is a contribution ceiling that dwarfs almost every other self-employed retirement plan — and a few features that look like they were designed for someone with a much bigger company. The Solo 401k self-employed explained: you wear two hats, and the IRS pays attention to both When you have a job, you defer some salary into a 401(k) and your employer maybe kicks in a match. Two separate buckets. A Solo 401(k) gives you both buckets at once, because you are both parties. The employee bucket (elective deferral): in 2026, you can defer up to $24,500 of your own pay (IRS Notice 2025-67). If you are 50 to 59 or 64+, add an $8,000 catch-up. If you are 60 to 63, the SECURE 2.0 super catch-up bumps that to $11,250 . The employer bucket (profit-sharing): on vetted of the deferral, your business can contribute up to 25% of compensation (roughly 20% of net self-employment income after the SE-tax adjustment). Stack those, and the combined total can reach the IRC §415(c) annual additions limit — $72,000 for 2026 , up from $70,000 the prior year. Catch-up contributions sit on vetted of that ceiling under IRC §414(v), so an older solo owner can go even higher. That §415(c) number is the headline. No SEP IRA gets there on the same income, because a SEP only has the employer bucket. The math that makes a SEP look small Say you net $150,000 from a single-member LLC. A SEP IRA caps you at roughly 20% of net SE income — call it about $28,000 . A Solo 401(k) on the same $150,000? You front-load the $24,500 employee deferral first, then add the profit-sharing piece on vetted — landing somewhere north of $50,000 in total contributions, depending on the exact net-earnings calculation. Same income. Nearly double the tax-advantaged savings. The difference is entirely the employee deferral that the SEP doesn't offer. That gap is the single most common thing a generalist accountant misses for solo clients. They set up a SEP because it is one form, and they never revisit it. Roth at the deferral level — the Solo 401k self-employed feature a SEP can't touch Here is the part nobody tells you. Your $24,500...
