How To Fix An Excess Contribution To A SEP-IRA Or Solo 401(k) Before The Penalty Hits

Remove the excess contribution plus any earnings it generated before your tax filing deadline, including extensions, to avoid a 6% annual penalty on the overage. If you’ve already filed your return, you generally cannot remove the excess and must pay the penalty until the overage is absorbed as a future-year contribution.

The exact cutoff for an excess SEP-IRA contribution fix

The dividing line is your tax-filing cutoff, including extensions, not the calendar year end. For a sole proprietor or single-member LLC, that’s April 15, 2025, for the 2024 tax year (or October 15, 2025, if you filed Form 4868). If you catch the overage before that date, you can pull the money out, report the earnings as income, and owe nothing beyond ordinary tax on those earnings. If you miss it, the IRS treats the excess as still in the plan, and you owe 6% of the excess amount for every year it remains there. That 6% is not a one-time fee, it recurs annually until the excess is absorbed by future contribution limits or you withdraw it in a later year (which itself triggers a 10% early distribution penalty if you’re under 59½). The trap is that many people assume "calendar year" means December 31; it doesn’t. The cutoff that matters is the one on your Form 1040, and extensions only help if you actually filed for one before April 15.

Why does this trigger Form 5330? Because the IRS considers an excess contribution to a SEP-IRA or solo 401(k) a prohibited transaction under Internal Revenue Code Section 4979. Form 5330 is the excise tax return used to report and pay that 6% tax. You don’t file it if you correct before the cutoff, you just process a normal corrective distribution. But once the cutoff passes, the form is mandatory, even if you later fix the excess in a future year. The penalty is calculated on the excess amount, not the earnings, so an overage costs $600 per year for every $10,000 of excess, every year, until resolved. That’s why the cutoff is the single most important fact in this entire process.

How to calculate and remove the excess without creating new problems

First, determine the excess. For a SEP-IRA, the limit is 25% of net self-employment income (or 20% of net profit after self-employment tax, which is the same number in practice). For 2024, the cap the IRS sets is $69,000; confirm the current-year cap at IRS.gov before you act. For a solo 401(k), add your employee deferral to the employer profit-sharing contribution (up to 25% of compensation). For 2024, the employee deferral limit the IRS publishes is $23,000, plus a $7,500 catch-up if 50 or older. If you contributed more than either cap, the excess is the difference. For example, if your solo 401(k) allows a $23,000 deferral plus an employer contribution of 25% of your net profit, and your net profit is $138,000, the employer piece the plan sets is $34,500. If you put in $60,000 total, your excess is $2,500. For a SEP-IRA, if your net profit is $80,000, your limit is $16,000 (20% of $80,000), so a $20,000 contribution leaves a $4,000 excess. The plan custodian publishes the exact contribution formula for your specific plan; open your plan document now and locate the employer-contribution section.

Second, calculate the net income attributable (NIA) on that excess. The IRS formula uses the account’s adjusted opening balance and the adjusted closing balance, but your custodian can do this for you. The formula is: NIA = excess × (adjusted closing balance − adjusted opening balance) / adjusted opening balance, where "adjusted" means the balance minus any prior excess contributions or plus any prior corrective distributions. You must remove both the excess and the NIA, if you only pull the excess, the earnings remain and count as a new contribution. Third, contact your custodian (Vanguard, Fidelity, Schwab, or whoever holds the account) and request a "corrective distribution of excess contributions plus earnings." Call the retirement-plan desk directly and say those exact words. They’ll provide the exact NIA calculation and cut you a check. You report the earnings on your tax return as ordinary income for the year you made the contribution, not the year you withdraw it. If the NIA is negative (the account lost value), you can remove less than the excess, and the loss reduces your deductible contribution for the year, but you still must remove the full excess amount.

When you cannot remove the money and must accept the penalty

The failure case is simple: if the tax-filing cutoff has passed, you cannot do a corrective distribution. The IRS does not permit retroactive fixes after that date, regardless of whether you filed an extension. You are now stuck with the excess in the plan, and you must file Form 5330 with your annual return, paying 6% of the excess for each year it remains. The only way out is to carry the excess forward as a contribution to a future year. For a SEP-IRA, that means reducing your contribution in a future year by the excess amount; for a solo 401(k), you reduce either the employee deferral or employer contribution in a future year. The 6% tax stops only when the excess is fully absorbed. If your custodian refuses to process the correction, some do, because they misinterpret the rules or require specific documentation, you’re still liable for the penalty, and you may need to close the account entirely to force the distribution, which triggers ordinary income tax and a 10% early withdrawal penalty if you’re under 59½.

There’s also a second failure case: you try to remove the excess after the cutoff but before filing your return, thinking the extension saves you. It doesn’t. The cutoff is the later of the tax-filing cutoff or the due date of your return, including extensions. If you filed for an extension, you have until October 15. But if you didn’t file for an extension and you missed April 15, you’re already in penalty territory. No amount of retroactive bookkeeping can undo that. The IRS will assess the 6% tax on the excess for the year it occurred, and you’ll file Form 5330 with a payment. If you ignore it, the IRS will send a notice, and the penalty compounds with interest. The practical takeaway: set a calendar reminder for March 1 every year to check your contribution limits against your actual net income, and if you’re self-employed with variable income, wait until you’ve filed your return to make the final contribution.

Frequently asked questions

Can I remove the excess from my solo 401(k) without closing the account?

Yes, but only if you do it before the tax-filing cutoff. Your plan administrator will process a corrective distribution, and you’ll receive a Form 1099-R for the earnings. The account itself stays open, and future contributions are unaffected. Call your plan administrator by March 1 of the year following the excess contribution and ask for a corrective distribution of the excess plus earnings.

What if my SEP-IRA lost money after I contributed too much?

You still remove the excess, but the NIA is negative. You remove the excess amount minus the loss, and the loss reduces your deductible contribution for the year. You don’t get a refund for the loss, it just lowers your tax deduction. Tell your custodian you need a corrective distribution with a negative NIA calculation and ask for the specific dollar figure you must withdraw.

Does the 6% penalty apply to both SEP-IRAs and solo 401(k)s equally?

Yes, the excise tax is identical under Section 4979. The calculation differs only in how the excess is defined, 25% of net income for a SEP-IRA versus combined deferral and profit-sharing limits for a solo 401(k). The penalty rate, the cutoff, and the carryforward rules are the same. When you evaluate self-employed retirement plans, the solo 401(k) vs sep-IRA comparison often turns on contribution ceilings, and the sep-IRA vs simple IRA comparison adds an employer-mandate variable, but the excess-contribution penalty mechanism is uniform across all three.

Can I avoid the penalty by recharacterizing the excess as a contribution to a different plan?

No. Unlike IRAs, you cannot recharacterize excess SEP-IRA or solo 401(k) contributions as if they were made to a different plan type. Your only options are a timely corrective distribution or paying the 6% tax and carrying the excess forward. If you have already passed the cutoff, file Form 5330 immediately and reduce next year’s contribution by the excess amount.

What happens if I file Form 5330 late but pay the tax?

The IRS will likely assess a late-filing penalty of 5% per month on the unpaid tax, up to 25%, plus interest. The 6% excise tax itself is separate. If you’re late, file Form 5330 immediately with a payment and a brief explanation; the IRS is more lenient when you self-report. Download Form 5330 from IRS.gov, attach a check for 6% of the excess, and mail it today.

The fix is mechanical, but the timing is unforgiving: miss the deadline by one day and you’re filing IRS Form 5330, writing a check for 6% of the excess, and dealing with a carryforward that complicates next year’s paperwork.

The one fact a competitor’s page won’t tell you: the IRS excess-contribution cutoff is not December 31 and not your extended filing date unless you actually filed Form 4868 before April 15, miss that pre-A