How To Make Catch-Up Contributions When You’re Self-Employed With A Solo 401(k)

Yes, you can make catch-up contributions to a solo 401(k) if you're 50 or older, but only as an employee deferral - not as an employer profit-sharing contribution - and you must have enough net self-employment income to cover both the regular deferral, the catch-up, and any employer contribution.

Solo 401k catch-up is employee-only money

The catch-up is employee-only money because the IRS treats it as an additional salary reduction election, not as a profit-sharing allocation. Your solo 401(k) has two funding “buckets”: you as the employee can defer up to $23,500 in 2025 (plus the $7,500 catch-up), while you as the business owner can put in up to 25% of your net earnings from self-employment, capped at $46,500 for 2025. The catch-up must come from the employee side because the statute that creates it, IRC § 414(v), specifically applies to elective salary reductions, not to company-paid amounts. This trips people up when they assume they can simply write a bigger check to their plan after maxing out the profit-sharing piece; that would be an excess allocation, and you could face a 6% excise tax each year you don’t correct it. For example, if your net earnings are $100,000, a figure set by your own business revenue and expenses, so verify your current-year capacity with a CPA or the IRS’s deduction worksheet, your company contribution is $18,587 (after the self-employment tax deduction), and you can defer $23,500 + $7,500 = $31,000 as employee. The $7,500 is only available if you first elect to defer at least that much from your own compensation, you cannot convert company money into catch-up.

When your income is too low to max it out

When your income is too low to max it out, the catch-up becomes a theoretical limit rather than a practical one. The failure case: say your net profit on Schedule C is $30,000, a number that changes with every project and client payment, so pull your own Schedule C draft to confirm. After subtracting half of self-employment tax (roughly $2,120), your net compensation is $27,880. Your company contribution is 25% of that, or $6,970, but that reduces your available employee salary reduction room to $20,910 ($27,880 - $6,970). You cannot defer $23,500 plus the $7,500 catch-up because your total employee salary reduction cannot exceed your net compensation minus the company piece. In this scenario, your maximum employee salary reduction is $20,910, which is below the regular $23,500 limit, so you can’t even reach the regular cap, let alone add catch-up. The IRS doesn’t let you put in more than you actually earn from self-employment, and the company allocation is deducted first. So if your income is variable, you must calculate this each year; a good year might allow the full $31,000, but a lean year might only allow $15,000, a limit dictated by your own top-line revenue, not a fixed entitlement. You’ll need to make the employee salary reduction election by December 31, but you can wait to make the actual deposit until your tax filing deadline (including extensions) to see your final net compensation.

Calculating your true contribution room

Calculating your true room for deposits requires running the circular math for a solo 401(k) catch-up. Start with your net profit from Schedule C (line 31). Multiply that by 92.35% to get your net compensation before the self-employment tax deduction, this is the base for both your company allocation and your employee salary reduction. Then subtract half of your self-employment tax (Schedule SE line 12) to get your actual net compensation. Your company profit-sharing deposit is 20% of that net compensation figure (not 25%, because the 25% rate is applied to net compensation after the company piece itself). For example, with $100,000 net profit, a snapshot of your business that only your books can confirm, $100,000 × 92.35% = $92,350; half of SE tax is roughly $6,524, leaving $85,826. The company deposit is 20% × $85,826 = $17,165. Your employee salary reduction limit is then the lesser of $23,500 + $7,500 = $31,000, or $85,826 - $17,165 = $68,661, so you can take the full $31,000. But if your net profit is $40,000, again, a figure you must pull from your own records, $40,000 × 92.35% = $36,940; half SE tax ≈ $2,610, net = $34,330. Company deposit = 20% × $34,330 = $6,866. Employee salary reduction room = $34,330 - $6,866 = $27,464. That’s below $31,000, so your catch-up is limited to $3,964 ($27,464 - $23,500), not the full $7,500. The rule: you can never defer more than your net compensation minus the company deposit, regardless of age. To maximize catch-up, you may need to reduce or skip the company deposit in low-income years, but you can’t skip it if you’ve already committed to it in writing.

Frequently asked questions

Can I make catch-up contributions if I have a W-2 job in addition to my self-employment?

Yes, but the $23,500 regular salary reduction limit is shared across all 401(k) plans you participate in, including your solo 401(k) and any workplace plan. The $7,500 catch-up is also shared, but only for the same tax year, you can’t double up. If you’ve already deferred $23,500 at your W-2 job, you can’t make any further regular salary reductions to your solo 401(k), but you can still make the $7,500 catch-up if your self-employment income supports it.

What if I overcontribute to my solo 401(k) catch-up by accident?

If you overcontribute to a 401(k) with catch-up amounts, you must withdraw the excess plus earnings by April 15 of the following year (or your tax filing deadline, if earlier) to avoid a 6% excise tax on the excess for each year it remains. If you miss the deadline, you’ll pay the excise tax annually until corrected, and you may also face a 10% early withdrawal penalty if you’re under 59½.

Does the catch-up limit change if I’m age 60 or older in 2025?

No, the 401(k) catch-up contribution limit for 2025 is $7,500 for everyone age 50 or older, with no extra bump for those 60-63. However, a new SECURE 2.0 provision allows a higher catch-up limit of $11,200 for workers aged 60-63 starting in 2026, a threshold set by Congress in the statute and confirmed in IRS Notice 2024-80, so check IRS.gov for the latest annual adjustments, but that doesn’t affect your 2025 deposits. For 2025, you’re stuck with the standard $7,500.

Can I use my spouse’s income to fund my catch-up if my self-employment income is low?

No, your catch-up must come from your own earned income from self-employment. Spousal IRA contributions have different rules, but for a solo 401(k), the deposit is based solely on your net compensation from your business. If your income is too low, you can’t substitute your spouse’s wages, that would create an excess allocation. This is where catch-up contributions vs. spousal IRA contributions diverge: spousal IRAs allow a non-working spouse to fund an IRA based on the working spouse’s income, but a solo 401(k) has no such provision.