2026 Solo 401k Contribution Limits by Age

If you are a high-income business owner or solopreneur, the Solo 401k offers the highest contribution limits of any defined contribution plan available to the self-employed. The reason is simple: in the words of the IRS, you are both the employee and the employer, which gives you access to multiple contribution buckets and total control over how much you set aside.

Below is a complete breakdown of the 2026 Solo 401k contribution limits by age, including employee deferrals, employer contributions, catch-up and super catch-up contributions, the overall limit, and how the Mega Backdoor Roth strategy unlocks far more Roth savings than a standard Roth IRA.

The Three Contribution Buckets

An advanced Solo 401k plan — like the one offered by My Solo 401k Financial — gives you three ways to contribute:

1. Employee Contributions

Also called salary deferrals, these can be made pre-tax or Roth and are subject to the annual employee deferral limit (plus catch-up contributions if you are age 50+).

2. Employer (Profit-Sharing) Contributions

Because you are also the employer, you control these contributions — unlike a 401k at a day job, where employer contributions are typically discretionary.

3. Voluntary After-Tax Contributions

This third bucket is the foundation of the Mega Backdoor Roth strategy. You first make a voluntary after-tax contribution, then transfer those dollars to a Roth Solo 401k or a Roth IRA.

2026 Solo 401k Contribution Limits by Age

The table below shows how the 2026 Solo 401k contribution limits change with age. Catch-up and super catch-up contributions are above and beyond the overall §415(c) annual additions limit.

Figures assume sufficient self-employment compensation to justify the contributions. The overall limit reflects the §415(c) annual additions limit plus applicable catch-up contributions.

Under Age 50

For 2026, the employee deferral limit is $24,500, and the overall §415(c) annual additions limit (employee + employer + voluntary after-tax) is $72,000.

Age 50 and Older (But Not 60–63)

Once you reach age 50, you can make an additional $8,000 catch-up contribution. This is a type of employee contribution, made directly to either the pre-tax or the Roth account. That brings the employee limit to $32,500 and the overall total to $80,000.

Age 60 to 63 — The Super Catch-Up

Thanks to the SECURE Act 2.0, individuals who are age 60 to 63 as of the end of 2026 can make a larger super catch-up contribution of $11,250 instead of $8,000. This raises the employee limit to $35,750 and the overall total to $83,250.

Mega Backdoor Roth: Supersize Your Roth Savings

The voluntary after-tax limit is dramatically higher than standard Roth limits. For 2026, a solopreneur with a plan that allows voluntary after-tax contributions can contribute 100% of self-employment compensation up to $72,000 as a voluntary after-tax contribution, then transfer those dollars to a Roth Solo 401k or a Roth IRA. That is almost ten times the $7,500 Roth IRA limit for 2026.

This two-step process — voluntary after-tax contribution followed by a transfer to a Roth account — is the Mega Backdoor Roth strategy. If you are age 50+ and want your catch-up dollars to be Roth, note that those go directly to the Roth account rather than through the after-tax bucket.

Day Job 401k + Solo 401k Side Hustle: How the Limits Interact

Many people have a day job 401k and a Solo 401k for a side business. Here is the general rule:

Employee Contributions Aggregate Per Person

The employee deferral limit (including catch-up contributions) applies at the person level. If you max out employee contributions at your day job, you cannot make additional employee contributions to your Solo 401k.

Employer & Voluntary After-Tax Apply Per Plan

Even if you’ve maxed out employee deferrals at day job 401k plan, you can still make employer and voluntary after-tax contributions to your Solo 401k. The $72,000 overall limit applies at the plan level and is not reduced by contributions to a day job 401k.