Investing Inside Your Solo 401(k): What to Actually Put in There

Picking a solo 401(k) provider gets most of the attention. Which one charges the lowest fees, which app is easiest to use, how fast the account opens. Then the account is open, the provider's site asks what to actually invest the money in, and that screen gets far less thought even though it matters more over 20 or 30 years. The provider mostly decides your paperwork. The fund choice decides your retirement.

The screen everyone clicks past

Every solo 401(k) provider presents a fund lineup or a brokerage window on day one, and most freelancers pick whatever is highlighted, or a target-date fund with the nearest year attached, and move on. That is not necessarily wrong. A target-date fund is a reasonable default. The problem is that a lot of providers also list higher-cost options on the same screen, sometimes actively managed funds from the same fund family, sometimes a "balanced" fund charging 10 times more for a similar mix of stocks and bonds. Nothing on the page flags which option is expensive. You have to know what to look for, and the expense ratio is the number that matters most.

Two kinds of solo 401(k), and only one gives you a real menu

A restricted fund lineup

Some providers, mainly banks, insurance companies and a few payroll platforms, build a solo 401(k) around their own proprietary fund lineup. You pick from a short list, often 10 to 20 funds, some of them index funds and some of them the provider's own actively managed products. Convenient, but the cheap options and the expensive options sit on the same menu with no warning label attached.

A full brokerage window

Other providers, notably Fidelity, Charles Schwab and E*TRADE, offer what is called a brokerage window. The plan itself is just a wrapper, and inside it you can buy almost any publicly traded fund or stock, the same way you would in a personal brokerage account. This is the more useful structure for most freelancers, because it lets you build the same low-cost lineup you would choose outside a retirement account, with no restricted menu narrowing the options.

Check your plan documents or call the provider before assuming you are stuck with an in-house lineup. Some solo 401(k) providers offer a brokerage window as an add-on that has to be requested separately from the base account, and it is worth the phone call.

What actually belongs inside the account

The honest answer for most freelancers is boring: one or two broad index funds, or a single target-date fund, and not much else. Here is how the common choices compare.

Fund type	What it actually is	Typical expense ratio	Ongoing effort
Total U.S. stock index fund	Owns nearly every publicly traded U.S. company, weighted by size	0.02% to 0.05%	Buy it, add to it
Total international stock index fund	Owns non-U.S. developed and emerging market companies	0.05% to 0.12%	Pairs with the U.S. fund
Total bond index fund	Owns a broad mix of U.S. government and investment-grade corporate bonds	0.03% to 0.07%	Sets the risk level
Target-date fund	One fund holding a version of all three above, shifting the mix as the target year nears	0.08% to 0.15%	Buy it once, done
Actively managed stock fund	A manager picks holdings, trying to beat an index	0.5% to 1.2% or more	Requires ongoing due diligence
Individual stocks	You pick specific companies yourself	No expense ratio, but no built-in diversification	Constant research and monitoring

The expense ratio ranges above are typical figures for broad, well-known index and target-date funds from providers such as Vanguard, Fidelity and Schwab, and will vary by fund and provider. The gap between the top three rows and the actively managed row is the whole story of this article.

Cost is the one variable you fully control

Nobody can guarantee what the market returns in a given year. Cost is different. It is printed in the fund's prospectus, it is charged automatically whether the market is up or down, and it compounds against your balance the same way a return compounds for it.

The evidence on active management is not close. Per S&P Dow Jones Indices' SPIVA U.S. Scorecard, about 86% of actively managed large-cap U.S. stock funds underperformed the S&P 500 over the trailing 10 years, through June 30, 2025 (checked Sept. 27, 2026). That is not a claim that every active manager fails every year. It is a reminder that paying more for a chance at beating a benchmark is, on average, paying more to fall short of it.

Three funds, or one fund, and calling it done

Two ways to build the lineup, and both are legitimate.

The three-fund portfolio: a total U.S. stock index fund, a total international stock index fund and a total bond index fund, in whatever proportion matches your age and comfort with risk. A common, simple starting point keeps the bond percentage well below your age for anyone decades from retirement, then raises it gradually as retirement gets closer. Rebalance once a year, whenever the proportions have drifted from your target.

The single target-date fund: pick the fund labeled with the year closest to when you plan to retire, and the fund manager handles the stock-to-bond shift automatically, rebalancing included. This is the true one-decision option, and it is a completely reasonable one, not a lesser one. Most large providers charge only a little more for it than for the individual index funds that make it up.

What you do not need is both approaches layered together, and you do not need a fourth or fifth fund added on top "in case." Once the first two or three funds already own thousands of companies and bonds between them, adding more funds is not adding diversification. It is usually just adding overlap and one more account to check.

Building the lineup this week

• Confirm whether your plan has a brokerage window or a restricted fund menu. Call the provider or check the plan document if the dashboard does not make it obvious.
• If you have a brokerage window, buy 2 to 4 funds: a total U.S. stock index fund, a total international stock index fund, a total bond fund (skip the bond fund entirely if you are decades from retirement and comfortable with the swings), or one target-date fund instead of all three.
• Check the expense ratio on every fund before buying, not after. Broad index funds commonly run 0.02% to 0.10%. Anything charging much above 0.5% deserves a specific reason.
• Turn on automatic dividend reinvestment so the account does not sit in cash between contributions.
• Set one calendar reminder, once a year, to check whether the stock-to-bond mix has drifted and needs rebalancing. Skip this step entirely if you chose a target-date fund.
• Ignore last year's best-performing fund on the menu. A fund's past return has close to no relationship with what it returns next.

Three habits that quietly cost freelancers money

New contributions sitting in a settlement or money-market fund for months, because income is lumpy and it feels safer to wait for a better entry point. The money is inside a tax-advantaged account either way. Sitting in cash there earns cash-like returns while giving up the growth the account exists to capture.

Overweighting the industry you already work in, because it feels familiar. A graphic designer loading up on a single software company's stock, or a driver loading up on a single rideshare company's stock, concentrates risk in the same industry that already pays the bills. If that industry has a bad year, the retirement account and the income both fall together.

Paying an advisor a percentage of assets every year to do what a target-date fund already does automatically for a fraction of the cost. That can be a legitimate service for a genuinely complicated financial life. For fund selection alone, most freelancers do not need it.

None of this requires predicting the market or picking a winning stock. It requires opening the account, choosing two or three funds that already own most of the market between them, keeping the cost low, and leaving it alone long enough for the compounding in the worked example above to run in your favor instead of against you.