Can You Have Both a Solo 401(k) and a Roth IRA?

Yes, you can contribute to both a Solo 401(k) and a Roth IRA in the same tax year. The IRS treats them as separate accounts with independent contribution limits, so funding one does not reduce what you can put into the other. For 2026, that means up to $72,000 in a Solo 401(k) plus $7,500 in a Roth IRA, with additional catch-up room if you are 50 or older.¹

Why the Two Limits Don’t Interact

A Solo 401(k) and a Roth IRA are governed by different sections of the tax code and different contribution ceilings. Nothing you put into one counts against the other.² The only real gatekeeper for the Roth IRA side is your income; the Solo 401(k) has no income ceiling at all.

They also work well together because the tax treatment is different. Traditional Solo 401(k) contributions reduce your taxable income today and are taxed when you withdraw in retirement. Roth IRA contributions are made with money you have already paid tax on, and qualified withdrawals in retirement come out tax-free.³ Holding both lets you choose which bucket to draw from in a given retirement year based on what your tax picture looks like then.

How Much You Can Put in a Solo 401(k) for 2026

The Solo 401(k) has the highest contribution ceiling of any retirement plan built for a one-person business. You contribute in two capacities: as the employee and as the employer.

On the employee side, you can defer up to $24,500 for 2026.⁴ On the employer side, you add a profit-sharing contribution. The combined total across both cannot exceed $72,000.¹

Catch-ups sit on top of that $72,000 ceiling. If you are 50 or older, you can add another $8,000, bringing the maximum to $80,000. Under SECURE 2.0, participants aged 60 through 63 get an enhanced catch-up of $11,250, for a maximum of $83,250.⁴

The Employer Contribution Math Depends on Your Business Structure

If you pay yourself W-2 wages through an S corporation, the employer contribution can be up to 25% of your W-2 compensation.⁵ That calculation is straightforward.

Sole proprietors and single-member LLCs run into a circular calculation instead. You start with net self-employment income, subtract half of your self-employment tax, and apply a reduced rate. For a plan with a 25% contribution rate, the effective rate lands at about 20% of your adjusted net earnings.⁶ The IRS publishes rate tables and worksheets. Underfunding costs you tax-deferred growth; overfunding triggers a correction process.

One boundary worth flagging: your total contributions can never exceed what you actually earned from the business. The $72,000 ceiling is a cap, not a floor.

How Much You Can Put in a Roth IRA for 2026

The Roth IRA contribution limit for 2026 is $7,500, with an extra $1,100 catch-up if you are 50 or older, for a total of $8,600.⁴

Unlike the Solo 401(k), the Roth IRA phases out at higher incomes. For 2026, the Modified Adjusted Gross Income ranges are:⁴

Single or head of household: full contribution below $153,000, reduced between $153,000 and $168,000, none above $168,000.
Married filing jointly: full contribution below $242,000, reduced between $242,000 and $252,000, none above $252,000.
Married filing separately (living with spouse): phase-out between $0 and $10,000, which effectively blocks most contributions.

Inside the phase-out range, the allowable contribution is reduced proportionally rather than eliminated all at once.

What If Your Income Is Too High for a Direct Roth Contribution

Being over the MAGI ceiling does not close off Roth savings. The backdoor Roth IRA is a two-step workaround: contribute to a traditional IRA on a nondeductible basis (there is no income limit for that), then convert the balance to a Roth IRA. There is no income cap on conversions.

The mechanics: open a traditional IRA, make the nondeductible contribution, wait for the funds to settle, and convert the full balance. Convert quickly, because any investment gains between the contribution and the conversion are taxable. Report both steps on IRS Form 8606 with your tax return.⁷

The trap is the pro-rata rule. If you already hold pre-tax dollars in any traditional, SEP, or SIMPLE IRA, the IRS aggregates all your traditional IRA balances and taxes the conversion proportionally. If 90% of your combined balance is pre-tax, then 90% of the conversion is taxable, even when you only contributed nondeductible dollars that year. A clean backdoor Roth generally requires a zero balance across those accounts before the conversion. A common fix is rolling existing traditional IRA funds into your Solo 401(k) first, since 401(k) balances are not counted in the pro-rata calculation.

A Third Bucket: The Roth Option Inside Your Solo 401(k)

Many Solo 401(k) plans allow a designated Roth account, which gives your employee deferrals Roth-style tax treatment with no income restriction.⁸ This is separate from a Roth IRA and stacks on top of it.

You can split the $24,500 employee deferral between pre-tax and Roth in any proportion. The combined total still cannot exceed the deferral limit, and the plan has to offer both options; a Roth-only 401(k) is not permitted. Once a contribution is designated as Roth, it cannot be reclassified as pre-tax later.⁸

Combining a Roth Solo 401(k) deferral with a separate Roth IRA yields up to $33,100 in Roth contributions for 2026 ($24,500 plus $8,600 at age 50 or older). The employer profit-sharing portion is always pre-tax.

Contribution Deadlines

Missing a deadline means the contribution does not count for that year.

Roth IRA contributions for a given tax year are due by April 15 of the following year. A tax return extension does not extend this deadline.² So 2026 contributions must be in by April 15, 2027.

Solo 401(k) employee deferrals depend on business structure. Sole proprietors and single-member LLCs can make employee deferrals up to their tax filing deadline. S corporations and partnerships must elect deferrals by December 31 of the contribution year.

Solo 401(k) employer contributions are due by the business tax return deadline, including extensions.⁵ For a sole proprietor who files an extension, that can push the deadline as late as October 15 of the following year, which gives you time to see full-year income before deciding how much to contribute.

What Happens If You Overcontribute

Excess contributions to a Roth IRA trigger a 6% excise tax on the excess amount for every year it remains in the account.⁹ The tax repeats annually until the excess is removed. You can avoid it by withdrawing the excess plus any earnings before your tax filing deadline, including extensions.¹⁰

Excess Solo 401(k) employee deferrals get taxed twice if not corrected: once in the year contributed, and again when eventually distributed. To avoid double taxation, take a corrective distribution of the excess plus allocable earnings by April 15 of the following year. That April 15 date is fixed; a tax extension does not move it.¹¹

1
Internal Revenue Service. 2026 Amounts Relating to Retirement Plans and IRAs, as Adjusted
2
Internal Revenue Service. Publication 590-A (2025), Contributions to Individual Retirement Arrangements (IRAs)
3
Internal Revenue Service. Roth IRAs
4
Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
5
Internal Revenue Service. One-Participant 401(k) Plans
6
Internal Revenue Service. Calculating Your Own Retirement Plan Contribution and Deduction
7
Internal Revenue Service. 2025 Form 8606
8
Internal Revenue Service. Retirement Plans FAQs on Designated Roth Accounts
9
Internal Revenue Service. Form 5329 – Additional Taxes on Qualified Plans (Including IRAs)
10
Internal Revenue Service. IRA Year-End Reminders
11
Internal Revenue Service. Consequences to a Participant Who Makes Excess Deferrals to a 401(k) Plan