Can a Spouse Have a Solo 401(k)?

Many self-employed business owners assume a Solo 401(k) can only cover one person.

In reality, a spouse who works in the same business can also participate, which can dramatically increase a household’s retirement savings potential.

For married entrepreneurs, consultants, and small business owners, this creates one of the most powerful retirement planning opportunities available.

This guide explains:

When a spouse can participate in a Solo 401(k)
How a spousal Solo 401(k) is structured
How couples can potentially double their retirement contributions
How each spouse can run their own Mega Backdoor Roth strategy

What Is a Spousal Solo 401(k)?

A Solo 401(k) (also called a one-participant 401(k)) is designed for businesses with no full-time employees other than the owners and their spouses.

If both spouses earn income from the same business, both may participate in the same plan and make contributions based on their own compensation.

This means:

✔ One Solo 401(k) plan
✔ Two participants (the spouses)
✔ Separate accounts for each participant

The business sponsors the plan, not the individual.

Example

If a married couple owns an LLC taxed as an S-Corporation, the LLC sponsors the Solo 401(k).

The result:

One plan document
Two plan participants
Separate participant accounts for each spouse

Why Separate Accounts Are Required

Even though both spouses participate in the same Solo 401(k), IRS rules require that each participant’s funds and contribution sources be tracked separately.

A properly structured self-directed Solo 401(k) typically maintains three sub-accounts per participant:

Pre-Tax Solo 401(k)
Roth Solo 401(k)
Voluntary After-Tax (Mega Backdoor Roth) account

Example Structure for a Married Couple

Participant	Pre-Tax	Roth	After-Tax
Spouse #1	Account	Account	Account
Spouse #2	Account	Account	Account

This results in:

1 Solo 401(k) plan
6 holding accounts

These accounts are typically held at a bank or brokerage firm and titled in the name of the Solo 401(k) trust for the benefit of each participant.

Doubling Retirement Contributions

When both spouses participate in the same Solo 401(k), each can make contributions based on their own earned income from the business.

This means a household may be able to double annual retirement savings.

Example

If both spouses earn income from the business:

Each spouse can make:

Employee contributions
Employer profit-sharing contributions
Catch-up contributions (if eligible)

This can result in very large annual contribution potential.

For example:

Contribution Type	Per Spouse
Employee contribution	Up to annual IRS limit
Employer contribution	Up to 25% of W-2 wages (S-Corp)
Catch-up contribution	Age-based eligibility

A married couple could potentially contribute twice the annual limit if both have sufficient earned income.

Mega Backdoor Roth for Each Spouse

One of the most powerful strategies available with a self-directed Solo 401(k) is the Mega Backdoor Roth.

This strategy allows participants to make voluntary after-tax contributions and convert them to Roth.

Because each spouse is a separate participant:

Both spouses can run their own Mega Backdoor Roth strategy.

Example

Jason and Sally operate an LLC taxed as an S-Corporation.

If each spouse receives the following in wages for tax year 2025:

$70,000 in W-2 wages

Each spouse could contribute:

$70,000 in voluntary after-tax contributions

Those funds could then be converted to:

Roth Solo 401(k)
Roth IRA

This strategy allows couples to rapidly build Roth retirement assets.

Roth Solo 401(k) vs Roth IRA Conversion

Historically, many individuals converted after-tax contributions to a Roth IRA.

However, recent legislation changed the landscape.

Under SECURE Act 2.0, Roth Solo 401(k) accounts:

✔ Are not subject to Required Minimum Distributions (RMDs)
✔ Offer additional plan flexibility

Because of this change, many investors now choose to convert Mega Backdoor Roth contributions into the Roth Solo 401(k) instead.

Participant Loans for Each Spouse

Another major advantage of a Solo 401(k) over an IRA is the ability to take a participant loan.

Each spouse can borrow from their own Solo 401(k) account balance.

IRS Loan Limits

Participants may borrow:

Up to 50% of their balance
Maximum $50,000

Example:

Participant	Account Balance	Maximum Loan
Spouse 1	$100,000	$50,000
Spouse 2	$100,000	$50,000

Total household borrowing potential:

$100,000

Loans typically must be repaid within 5 years, unless used to purchase a primary residence.

Can a Spouse have a Solo 401k_

Pooling Funds for Investments

Although each spouse maintains separate accounts, the funds can still be combined for investments.

This is common with self-directed Solo 401(k) plans, which allow investments such as:

Real estate
Private equity
Promissory notes
Precious metals
Cryptocurrency
Stocks and ETFs

Example:

Participant	Balance
Spouse 1	$150,000
Spouse 2	$150,000

Total investment capital:

$300,000

The investment would be titled in the name of the Solo 401(k) plan for the benefit of both participants.

Why a Spousal Solo 401(k) Is So Powerful

For married entrepreneurs, a spousal Solo 401(k) provides significant advantages:

✔ Potential to double annual retirement contributions
✔ Ability to run two Mega Backdoor Roth strategies
✔ Access to two participant loans
✔ Ability to pool funds for larger investments
✔ Flexibility to invest in stocks and alternative assets

A properly structured self-directed Solo 401(k) allows couples to maximize tax-advantaged retirement savings while maintaining full investment flexibility.