Key takeaways

• The 2026 Solo 401(k) overall limit is $72,000, and an $8,000 catch-up contribution (or $11,250 super catch-up at ages 60 to 63) raises it to $80,000 or $83,250.
• Solo 401(k) for partnerships starts from self-employment compensation, which equals Schedule K-1 Box 14 Code A income minus one-half of self-employment tax.
• A partner under age 50 needs $252,317.72 of Box 14 Code A income to make $72,000 of pre-tax contributions: a $24,500 employee deferral plus a $47,500 employer contribution.
• A partner whose day-job plan already uses the $24,500 employee limit needs $376,480.35 of K-1 income to make a $72,000 pre-tax employer contribution.
• A $72,000 voluntary after-tax contribution for a Mega Backdoor Roth needs only $77,473.32 of K-1 income, because it is not limited to a percentage of pay.
• A partner age 50 to 59 or 64+ needs $86,081.46 of K-1 income to make $80,000 of Mega Backdoor Roth plus Roth catch-up contributions in 2026.
• A partner age 60 to 63 needs $89,578.52 of K-1 income to make $83,250 of Mega Backdoor Roth plus Roth super catch-up contributions in 2026.
• The SECURE 2.0 Roth catch-up mandate applies to W-2 FICA wages above $150,000 for 2025, so partners reporting K-1 income are not forced into Roth catch-ups.

How much partnership income do you need to max out a Solo 401(k) in 2026?

Solo 401(k) for partnerships has no single income threshold, because the K-1 income a partner needs depends on which contribution type the partner wants to maximize.

The table lists the minimum Schedule K-1 Box 14 Code A income for each 2026 goal, as calculated in the webinar.

What are the 2026 Solo 401(k) contribution limits?

Solo 401(k) for partnerships uses four 2026 limits: the employee limit, the catch-up amounts, the 20% employer limit, and the overall limit.

A Solo 401(k) holds three contribution buckets. The employee bucket and the employer bucket are the traditional two. The third bucket is the voluntary after-tax contribution, which supports Mega Backdoor Roth Solo 401(k) contributions.

How do you calculate self-employment compensation from Schedule K-1 Box 14 Code A?

Solo 401(k) for partnerships measures every limit against self-employment compensation, which is Box 14 Code A income minus one-half of self-employment tax.

The solo 401(k) exists so a self-employed person can save earned self-employment income. A participant cannot save more than the participant earns.

What counts as Solo 401(k) income for a partnership?

• Earned self-employment income reported in Box 14 Code A of Schedule K-1.
• Guaranteed payments for services, when they are reported in Box 14 with the right code.
• Income of active general partners and managing LLC members.

What does not count?

• W-2 wages from a day job.
• Investment income, such as Schedule E rental income.
• Owner income that is not earned self-employment income.
• Distributive shares of limited partners under IRC § 1402(a)(13), and income of capital-only partners who perform no services.
• Entity gross revenue before business expenses.

How much K-1 income does a partner need for $72,000 of pre-tax contributions?

Solo 401(k) for partnerships requires $252,317.72 of Box 14 Code A income for a partner under age 50 to make $72,000 of pre-tax employee and employer contributions.

After one-half of self-employment tax, that income leaves $237,500 of self-employment compensation. The partner contributes 100% of compensation up to the $24,500 employee limit. The employer contribution is 20% of $237,500, which is $47,500. Together the two total $72,000.

Does the K-1 income change with catch-up contributions?

Solo 401(k) for partnerships needs the same $252,317.72 at every age for the pre-tax scenario. The employee deferral rises to $32,500 with the $8,000 catch-up, and the employer contribution stays at $47,500. The total becomes $80,000. At ages 60 to 63, the $11,250 super catch-up lifts the total to $83,250.

Does the Roth catch-up mandate apply to partners using a Solo 401(k)?

Solo 401(k) for partnerships does not force Roth catch-up contributions unless the partner receives W-2 wages from the sponsoring business.

SECURE 2.0 requires participants with W-2 FICA wages above $150,000 for 2025 to make catch-up contributions as Roth contributions. Partners receive and report earned self-employment income on Schedule K-1 Box 14, not W-2 wages.

Partners therefore keep the option to make catch-up contributions pre-tax. Roth catch-up contributions remain allowed under the My Solo 401k Financial plan but are not mandated. A partner’s separate W-2 job with an unrelated employer is tested under that employer’s plan only.

How much partnership income is needed if a day-job 401(k) already uses the employee limit?

Solo 401(k) for partnerships limits employee contributions across every plan a partner joins, so a maxed day-job 401(k) leaves only the employer bucket for pre-tax savings.

The employer contribution limit is 20% of self-employment compensation. A $72,000 employer contribution therefore requires $360,000 of compensation. Reaching $360,000 after one-half of self-employment tax requires at least $376,480.35 in Box 14 Code A.

How much K-1 income does a partner need for Mega Backdoor Roth contributions?

Solo 401(k) for partnerships supports a $72,000 Mega Backdoor Roth contribution with $77,473.32 of K-1 income because voluntary after-tax contributions are not a percentage of pay.

The Mega Backdoor Roth is a two-step process. First, the partner makes a voluntary after-tax contribution. Second, the partner converts it to Roth, either in the plan to the Roth Solo 401(k) or out of the plan to a Roth IRA.

The partner still subtracts one-half of self-employment tax first, so the K-1 figure exceeds the compensation figure.

What K-1 income does each age band need?

• Under age 50: $77,473.32 supports a $72,000 voluntary after-tax contribution.
• Age 50 to 59 or 64 and older: $86,081.46 supports $80,000, which adds the $8,000 catch-up.
• Age 60 to 63: $89,578.52 supports $83,250, which adds the $11,250 super catch-up.

How is a Solo 401(k) for partnerships set up with multiple partners?

Solo 401(k) for partnerships uses a single plan sponsored by the partnership, with a separate account for each partner and each fund type.

The partnership can sponsor the plan when it has no non-owner, non-spouse employees. Each partner must also report their own earned self-employment income in Box 14 of Schedule K-1. \

Each partner chooses their own contribution types and amounts, subject to the limits and deadlines. One partner may maximize Roth while another maximizes pre-tax. Two partners who each want pre-tax, Roth, and after-tax money need six accounts in total. \

How do you make Mega Backdoor Roth and catch-up contributions in practice?

Solo 401(k) for partnerships handles Mega Backdoor Roth and catch-up contributions through at least two accounts at the participant’s bank or brokerage, such as Fidelity or Schwab.

A Roth account receives the catch-up contribution. A separate after-tax account receives the voluntary after-tax contribution. The participant then moves the after-tax money to the Roth Solo 401(k) or to a Roth IRA, including one the participant already owns.

Can Roth Solo 401(k) money move out to a Roth IRA?

Roth Solo 401(k) money generally needs a triggering event, typically age 59½, before it can move out of the plan. Voluntary after-tax contributions are an exception. Anyone can transfer them to a Roth IRA when the plan allows it.

This article is based on the November 4, 2026 live webinar hosted by My Solo 401k Financial.