Fidelity Self Employed 401k Won’t Let You Convert to Roth? Do This Instead

If you have a Fidelity self-employed Solo 401k, you may have discovered a frustrating limitation: Fidelity’s prototype plan documents do not allow in-plan Roth conversions. That means you cannot take pre-tax money already sitting in your Solo 401k and move it into a Roth Solo 401k account to benefit from tax-free growth — at least not with Fidelity’s own plan documents. The same limitation applies to other discount brokerage Solo 401k plans, including Schwab.

In this guide from My Solo 401k Financial, we explain exactly why this limitation exists, what an in-plan Roth conversion is, and — most importantly — how you can unlock this powerful feature while keeping your investments and accounts at Fidelity.

What Is an In-Plan Roth Conversion?

An in-plan Roth conversion is the process of taking money that is already inside your Solo 401k — money that was contributed on a pre-tax basis — and converting it to a Roth Solo 401k account within the same plan. Once converted, those funds now enjoy the potential for tax-free growth, just like any other Roth account.

When you process an in-plan Roth conversion, the converted amount is treated as taxable income in the year of conversion. This is why many individuals strategically time conversions for years when their income — and therefore their tax bracket — is relatively low. Paying taxes now at a lower rate in exchange for tax-free growth later can be a powerful long-term wealth-building strategy.

Why Fidelity’s Self-Employed Solo 401k Blocks In-Plan Roth Conversions

The reason Fidelity’s self-employed Solo 401k does not permit in-plan Roth conversions comes down to one word: documents. Fidelity uses what are called prototype plan documents — their own standardized plan paperwork — to govern the Fidelity self-employed Solo 401k. Those prototype documents simply do not include a provision allowing in-plan Roth conversions.

This is not unique to Roth conversions. Fidelity’s prototype plan also does not support several other advanced Solo 401k features, including the Mega Backdoor Roth, participant loans, and certain investment flexibility options. The plan documents are the foundation of every Solo 401k — whatever the documents do not permit, the plan cannot do.

Fidelity Prototype Plan vs. Advanced Solo 401k Plan — Feature Comparison

The Solution: Upgrade to a Third-Party Solo 401k Plan (and Keep Your Fidelity Account)

The good news is that you do not have to leave Fidelity. Fidelity allows individuals to open what is called a Fidelity Investment Only Account (formerly called a non-prototype account) — a special account type specifically designed for people who bring their own third-party plan documents to Fidelity.

This means you can adopt an advanced Solo 401k plan document from My Solo 401k Financial, keep all of your existing investments and cash at Fidelity in the new Investment Only account, and immediately gain access to in-plan Roth conversions and all of the other advanced features your old Fidelity prototype plan could not provide.

What Else Does Upgrading Your Solo 401k Plan Unlock?

When you upgrade from Fidelity’s prototype plan to an advanced Solo 401k plan document from My Solo 401k Financial, you gain access to a full suite of features that go well beyond in-plan Roth conversions. Here are some of the top features that prompts solopreneurs to upgrade their basic Fidelity Solo 401k plan:

Mega Backdoor Roth — Up to $72,000 in Roth Contributions for 2026

The Mega Backdoor Roth strategy allows self-employed individuals to contribute up to $72,000 (or more for those age 50 and older) to a Roth account through voluntary after-tax contributions to the Solo 401k. These funds end up in a Roth Solo 401k or Roth IRA, where they have the potential for tax-free growth. This strategy is completely unavailable under Fidelity’s prototype plan documents but is fully supported by My Solo 401k Financial’s advanced plan.

Solo 401k Participant Loans

With an advanced plan, you can borrow from your own Solo 401k — up to 50% of your account balance, not to exceed $50,000 — and use the funds for any purpose. The loan is not subject to taxes or penalties as long as it is properly documented as a loan and repaid according to a schedule. Repayments are made in equal monthly or quarterly installments of principal and interest, with interest set at either prime plus 1% or a CD rate plus 2%, spread over a five-year term. My Solo 401k Financial handles all loan documentation requirements at no additional charge.

Alternative Investments — Real Estate, Private Equity, and Crypto

Standard brokerage-type investments like mutual funds, ETFs, certificates of deposit, and publicly traded stocks are always available. But with an advanced Solo 401k plan document, you also gain the ability to invest in real estate, private equity, and cryptocurrency. Even through a Fidelity Investment Only Account, you can wire funds out to make alternative investments. For direct crypto purchases on an exchange, a separate exchange account is required.

$1,500 in SECURE Act Tax Credits

Upgrading to an advanced plan from My Solo 401k Financial also makes the solopreneur eligible to claim $1,500 in SECURE Act tax credits — $500 per year for three consecutive years. This credit alone more than covers My Solo 401k Financial’s fees for the first seven years.

How the Upgrade Process Works — Step by Step

Transitioning from Fidelity’s prototype plan to an advanced plan from My Solo 401k Financial is a streamlined process. Here is how it works:

My Solo 401k Financial Pricing — And Why the Tax Credits More Than Cover It

My Solo 401k Financial charges $650 as the initial cost, which includes the $525 establishment fee plus the first annual fee of $125. Starting twelve months later, the annual fee of $125 applies each year going forward.

Consider this against the $1,500 in SECURE Act tax credits ($500 per year for three years) that become available when you upgrade to an advanced plan. Those credits alone more than cover My Solo 401k Financial’s fees for the first seven years — making the upgrade effectively a net-positive from a cost standpoint before you even account for the tax savings from Roth conversions and the Mega Backdoor Roth strategy.

The Foundation Is Always the Plan Documents

It is worth emphasizing: every Solo 401k feature — whether it’s an in-plan Roth conversion, the Mega Backdoor Roth, participant loans, or alternative investments — is only possible if the plan documents explicitly permit it. The plan document is the legal governing instrument of the Solo 401k. If the documents don’t allow it, neither does the plan — regardless of what the brokerage offers.

This is exactly why upgrading plan documents is the first and most critical step. Once you have advanced plan documents from My Solo 401k Financial in place, Fidelity (or any other brokerage) is simply the custodian holding the assets — and the brokerage is happy to accommodate the advanced features because the legal authority to do so resides in your plan documents, not in Fidelity’s prototype template.