Solo 401(k) Contributions Can Save You $30,000+ in Taxes This Year

On a recent episode of NerdWallet’s Smart Money Podcast titled Is College Worth It in 2026? Plus, How to Split Solo 401(k) Contributions to Save More, the host made a claim that gets attention fast: “By putting $72,000 in, you basically get a $30,000-plus tax benefit.” The pitch is that a self-employed earner can shovel up to $72,000 into a Solo 401(k), skip tax on every dollar of it this year, and let it grow tax-deferred until withdrawal.

The stakes matter because that headline number assumes a tax profile most self-employed Americans do not have. If you act on it without checking the math, you can easily over-contribute, mis-elect Roth versus traditional, or expect a refund check that never arrives.

The Verdict: Right Math, Narrow Audience

The claim is mathematically correct, but it only lands for a specific profile: a top-bracket earner in a high-tax state. To save $30,000-plus on a $72,000 contribution, your combined federal and state marginal rate has to clear roughly 42%. That requires the 37% federal bracket plus meaningful state tax on top.

Consider a self-employed software consultant in California netting $700,000. Her top federal marginal rate is 37%; California adds roughly 13.3% at the top; and she also crosses the 3.8% net investment income/Medicare surcharge threshold. A $72,000 pre-tax Solo 401(k) contribution, fully deductible against ordinary income, removes that money from a combined marginal stack north of 50%. The first-year tax reduction is closer to $36,000. The host’s number is, if anything, conservative for her.

Now run the same contribution for a freelance designer in Texas, netting $160,000. Her federal marginal rate is 24%, Texas charges no state income tax, and her tax savings on a $72,000 contribution to land near $17,000.

One more wrinkle the quote glosses over: You cannot just write a $72,000 check. The Solo 401(k) cap combines an employee deferral plus an employer profit-sharing piece tied to net self-employment income. Hitting the full $72,000 generally requires net business income well into the low six figures.

Where the Strategy Pays Off, and Where It Backfires

The traditional pre-tax Solo 401(k) is the right choice for self-employed earners in the top federal bracket living in California, New York, or New Jersey, with stable peak earnings and a realistic expectation of a lower bracket in retirement. As the host put it, “It’s probably a pretty safe bet that you’re in the highest tax bracket that you’re ever going to be in.”

It works against you if you are in the 22% or 24% bracket today with a fast-growing business. CPI is sitting at 330.3, and the fed funds upper bound is near 4% point to a still-elevated price level that future tax policy may have to reckon with. If your bracket is likely higher in 10 years, the Roth Solo 401(k) wins, even though it offers no upfront deduction.

What to Do This Week

1. Calculate your true combined marginal rate (federal + state + SE Medicare surcharge). Multiply by $72,000 to see your actual ceiling on tax savings, not the podcast’s.
2. Pull your year-to-date net self-employment income and confirm you can support the employer profit-sharing side of the contribution before you target the full cap.
3. Decide traditional vs. Roth using bracket trajectory: top bracket in a high-tax state today goes traditional; lower bracket with a fast-scaling business goes Roth.
4. Open and fund the plan on time. The employee deferral election generally must be in place by December 31; employer contributions can follow up to your tax filing deadline.

The quote gets the upside right for the people it describes and overstates it for everyone else; the only number that matters is your own marginal rate against your actual contribution capacity.