Setting Up a Solo 401(k): A Step-by-Step Guide for Freelancers

More freelancers know about the Solo 401(k) than actually have one. The tax advantages are well understood at this point: shelter up to $70,000 of income per year, reduce your taxable income dollar-for-dollar, and let those dollars compound tax-deferred for decades. What trips people up is the setup. There is a vague sense that it involves paperwork, plan documents, and financial institutions, and at some point that vague sense becomes a reason to put it off until next year.

The reality is that opening a Solo 401(k) at a major brokerage takes about 20 minutes of active effort and another week of waiting for account approval. The hardest part is knowing which steps happen in which order. This guide walks through exactly that.

Who Can Open a Solo 401(k)?

You qualify for a Solo 401(k) if you have self-employment income and no full-time employees other than a spouse. That covers a wide range of situations: sole proprietors, single-member LLCs, freelancers, independent contractors, gig workers, and side-hustlers who also have a W-2 job from an employer. The W-2 job doesn't disqualify you. What matters is that you have some net income from self-employment and aren't running a business with employees on payroll.

One common edge case: if you have a part-time employee who works fewer than 1,000 hours per year, you may still qualify. The exact threshold depends on the plan documents, so if you have any employees at all, confirm with the brokerage before applying.

A spouse who also works in your business can participate in the same Solo 401(k), which effectively doubles the household contribution limit. That is a significant advantage worth knowing about if it applies to you.

The Six Steps to Open Your Account

1. 1
   Confirm your net self-employment income for the year

   Your contribution limits are calculated based on your net SE income, specifically 92.35% of net profit (the "SE base"). Before you can decide how much to contribute, you need a reasonable estimate of what you will earn this year. You don't need exact figures yet, but you do need a ballpark to avoid over-contributing. A quick estimate: take your expected gross revenue, subtract your expected deductible business expenses, and multiply by 0.9235. That is your SE base. Your maximum employer contribution is 25% of that number, capped so the total stays under $70,000.

2. 2
   Choose a brokerage

   Pick where you want the account held. The main considerations are whether the plan allows Roth contributions, what investment options are available, and whether there are any account fees. See the brokerage breakdown below. For most freelancers with no strong existing relationship with any particular institution, Fidelity is the most commonly recommended starting point.

3. 3
   Complete the application and plan adoption agreement

   This is where most people expect complexity and find surprisingly little. Major brokerages have moved their Solo 401(k) applications almost entirely online. You will enter your name, address, Social Security number or EIN, business name, business structure (sole proprietor, LLC, etc.), and basic income information. You will also select whether you want a Roth option and whether you want loan provisions included in the plan. Most people leave loan provisions off unless they expect to need them. The application generates a plan document package that serves as the legal basis of your 401(k).

4. 4
   Sign and return the plan adoption documents

   After completing the online application, you will receive a plan adoption agreement to sign. This is the document that legally establishes the plan. At Fidelity and Schwab, this can be done with an electronic signature. Some brokerages still require a wet signature and mailing the form back. Read the instructions carefully. The date you sign the adoption agreement is typically treated as the plan establishment date for IRS purposes, which is why this step needs to happen before December 31.

5. 5
   Fund the account with your first contribution

   Once the account is approved and open (usually within a few business days to two weeks depending on the brokerage), you can transfer funds in. You have two contribution types to decide on: the employee elective deferral ($23,500 max for 2026, or $31,000 if you're 50 or older) and the employer profit-sharing contribution (up to 25% of your net SE income). Employee contributions must be deposited by December 31. Employer contributions can be deposited as late as your tax filing deadline, including extensions, so you have more flexibility there. Many people make a lump-sum contribution once they have finalized their year-end numbers, rather than contributing throughout the year.

6. 6
   Choose your investments

   Money sitting in a 401(k) account earns nothing until you actually invest it. This step trips up a surprising number of people who open the account and then forget to select funds. At minimum, pick a target-date fund matching your expected retirement year (for example, a 2055 fund if you're in your early 30s) if you don't want to think about asset allocation. If you want more control, low-cost index funds tracking the total U.S. stock market, international stocks, and bonds are the standard building blocks. The exact investment decision is beyond the scope of this article, but the key action is: don't leave the money sitting uninvested in a money market default.

Where to Open Your Solo 401(k): Brokerage Options

A few years ago, the standard advice was to compare Fidelity, Vanguard, and Schwab. That comparison has changed. In 2023, Vanguard discontinued new Individual 401(k) applications and directed existing customers to Ascensus, a third-party retirement plan administrator. If you already have a Vanguard Solo 401(k), it likely transferred to Ascensus. If you are opening a new one, Vanguard is not an option. Here is where things actually stand for new accounts in 2026:

The Deadlines That Matter

The deadline structure for a Solo 401(k) is one of the most commonly misunderstood aspects of the account. Employee and employer contributions have different deadlines, and the plan establishment deadline is separate from both.

The December 31 plan establishment deadline is hard. If you miss it, you cannot retroactively create a Solo 401(k) and claim contributions for the prior year. The SECURE Act of 2019 created a limited exception that allows employer-only (profit-sharing) contributions to be made to a plan established after year-end but before your filing deadline, but this exception applies only to employer contributions. If you want to make employee elective deferrals for 2026, the plan must exist by December 31, 2026, and the contribution must also be deposited by that date.

A practical note: if you are reading this in the fall and haven't opened your account yet, do not wait until late December. Brokerage processing times can run one to two weeks, and some institutions have internal holiday cutoff dates for new account approvals. Submitting an application on December 28 is a gamble. October or November is a much safer target.

What Happens If You Miss December 31?

If December 31 passes and you don't have a plan established, your options for sheltering self-employment income in a tax-advantaged retirement account narrow considerably. A SEP-IRA is the main alternative: you can open and fund a SEP-IRA all the way up to your tax filing deadline (including extensions), which gives you until April 15 or even October 15 to act. The trade-off is that SEP-IRA contributions are employer-only, capped at 25% of net SE income (versus the Solo 401(k)'s higher combined limit), and SEP-IRAs don't allow Roth contributions.

For a freelancer earning $60,000 in net SE income, the SEP-IRA limit would be roughly $13,000 (25% of the SE base of approximately $55,400). A Solo 401(k) with the same income could shelter up to $34,500 or more, combining the $23,500 employee deferral with an employer contribution. The difference is meaningful, especially for someone earlier in their career trying to accumulate savings quickly.

The short version: if you miss December 31, use a SEP-IRA as a fallback for that year, and open the Solo 401(k) immediately in January so you're in position for the next tax year.

After You Open the Account: Staying on Track

Opening the account is the hardest step for most people. Once it's done, the ongoing maintenance is light. A few things to keep up with:

Designate a beneficiary. Most brokerages prompt you to do this during setup, but confirm it is on file. A retirement account without a named beneficiary can create complications for your estate.

Keep contribution records. Track the date and amount of each contribution, and whether it was classified as an employee deferral or employer profit-sharing. This distinction matters when you file Schedule 1 and Form 8880 (if applicable), and it matters if you are ever audited.

Watch the Form 5500-EZ threshold. Once your Solo 401(k) plan assets exceed $250,000 at the end of any plan year, you are required to file Form 5500-EZ annually. It is not a complicated form, but the penalty for forgetting to file it is steep: $250 per day, up to $150,000. Set a calendar reminder to check your account balance in early January each year.

Reassess contributions annually. Your net SE income varies year to year, which means your maximum employer contribution changes. Run the calculation each fall using your best income estimate for the year, then top up before the deadlines. If you have been deferring from each payment throughout the year, do a final reconciliation in November or December to make sure you haven't over- or under-contributed.