How to Choose a Solo 401(k) Provider: A CPA’s Framework

A solo 401(k) provider may supply the investment account, the plan document, and help with the annual administration. Some providers handle all three. Others leave part of the work to you.

Before opening an account, compare the features you need, the total cost, and who will handle each responsibility.

First, confirm that the plan fits your business

A solo 401(k) is a regular 401(k) used by a business whose plan covers only eligible owners and their spouses. It still needs a written plan document, accurate contribution records, and any required tax filings.

Your contribution limit depends on your business income and the applicable tax rules. If you also contribute to a 401(k) through another job, your employee contribution limit is generally shared across those plans. Opening another account does not give you a second employee contribution limit.

If your business has employees, or you expect to hire, review their eligibility before choosing an owner-only plan.

Compare what the provider actually includes

An investment account, a plan document, and ongoing administration may be offered together or purchased separately. Use the same questions when comparing providers so you can see what each fee covers.

What to compare	What to find out
Investments	Which investments are available, where the assets are held, and what account and investment fees apply.
Plan document and updates	Who supplies the document, keeps it current when the law changes, and explains any action you need to take.
Roth features	Whether the plan allows Roth employee contributions, separate after-tax contributions, and Roth conversions.
Loans	Whether participant loans are allowed, what they cost, and who tracks the repayments.
Annual administration	Who checks contribution limits, maintains plan records, and prepares and files Form 5500-EZ when required.
Adding employees	Whether the provider can support a plan covering employees and what would change in the services and fees.
Total cost	Setup, annual, investment, loan, document-update, transfer, and termination charges.

Check the service agreement before choosing. A provider may supply the plan document without taking responsibility for the annual filing or contribution calculations.

Check which Roth features are available

Roth employee contributions and separate after-tax employee contributions are different features. A plan that offers Roth contributions does not necessarily support a “mega backdoor Roth” strategy.

That strategy requires the plan to accept non-Roth after-tax employee contributions and provide an available way to move the money into Roth treatment. Depending on the plan, that could mean an in-plan Roth rollover or an eligible distribution rolled into a Roth IRA. Earnings and other pretax amounts can create taxable income when converted.

If this feature matters to you, confirm both parts before opening the plan: the after-tax contribution and the conversion or rollover route.

Know who handles Form 5500-EZ

For the usual annual filing test, add together the year-end assets of all one-participant plans your business maintains. If the combined total exceeds $250,000, a Form 5500-EZ filing is generally required. The test is not based on each account separately.

A final return is required for the year all plan assets are distributed or transferred, even if the balance is below that threshold. Deciding to close the plan and completing the distributions can happen in different years.

Confirm who determines whether a return is needed, who prepares it, and who files it. The IRS Form 5500-EZ instructions explain the filing requirements.

Think ahead about employees and other businesses

When an employee becomes eligible to participate, the plan must address that coverage. The 401(k) can continue, but an arrangement designed only for owners may need changes to its documents, administration, and reporting.

Part-time employees can also become eligible. Employees of another business you or your spouse own may affect the analysis under the rules for related businesses.

Ask about this before hiring or expanding. Find out whether the provider can support the change and what it would cost.

Understand the limits of extra flexibility

An IRS pre-approved document allows certain choices, but customization is limited. IRS approval concerns the plan language. It does not establish that your plan is being operated correctly or that its investments are approved.

Participant loans must follow the plan document and tax rules. Alternative investments, such as real estate, also require care. A self-directed account does not remove restrictions on personal use or transactions involving the owner and other related parties.

Choose the services you will use

Compare a few providers using the same features and responsibilities. A lower fee may leave more administration with you. A higher fee is useful only if it includes services you need.

After choosing, continue reviewing the fees, plan updates, and work the provider has agreed to handle. Hiring help does not remove the business’s responsibility to operate the plan correctly.

This article provides general information. Plan terms, tax rules, and provider services should be reviewed for your circumstances.