What Is the Penalty for Over-Contributing to a 401(k)?

The penalty for over-contributing to a 401(k) isn’t a flat fine. It’s double taxation: the excess amount is taxed once in the year you contributed it and taxed again when you eventually withdraw it in retirement. You can avoid the second tax hit by having the excess distributed from your plan by April 15 of the year after the over-contribution, but that deadline is firm and doesn’t move if you file a tax extension.

The 2026 Limit You Can Go Over

The IRS caps how much you can defer into all your 401(k)-type plans combined each year. For 2026, the standard elective deferral limit is $24,500, up from $23,500 in 2025.¹ If you turn 50 or older during 2026, you can defer an additional $8,000 in catch-up contributions, for a ceiling of $32,500.²

A higher catch-up applies if you’re 60, 61, 62, or 63 during the calendar year. Under a SECURE 2.0 change, this group can defer an extra $11,250 instead of the standard $8,000, for a combined ceiling of $35,750 in 2026.²

The ceiling that matters is the one that applies to you personally across every plan you’re in. Salary deferrals into a 401(k), a 403(b), a SARSEP, and a SIMPLE IRA all count toward the same annual limit.³ Two separate employers have no way to coordinate, so tracking the total falls on you.

How People End Up Over the Limit

The most common scenario is a mid-year job change. You contribute $15,000 at your first employer, start a new job, and the new payroll system has no knowledge of the prior deferrals. You set your contribution rate to max out the new plan, and by December you’ve deferred $34,000 combined when your limit was $24,500. Each plan followed its own rules. Together they pushed you over.

Working two jobs at once creates the same problem. Neither plan administrator sees what you’re deferring at the other employer. Catch-up eligibility is another trap: someone who turns 50 in January may plan around the extra $8,000, and the arithmetic gets tangled if the standard maximum was already hit earlier in the year. The IRS holds you, not the plan, responsible for the aggregate.

Fixing an Excess Deferral Before April 15

The statute gives you a two-step window. First, by March 1 of the year after the excess, you notify the plan administrator in writing, specifying how much of the excess you want that plan to distribute.⁴ If two plans caused the problem, you pick which one distributes. Most people choose the plan with the worse investment options or no employer match, though you can split the correction between plans.

Second, the plan must distribute the excess plus any earnings on it by April 15. That date is fixed. A tax extension does not move it.⁵ The plan calculates gains or losses on the excess through the end of the year the excess occurred, and the corrective distribution includes both the original excess and those earnings.

A 2026 excess means you notify by March 1, 2027, and the money is out by April 15, 2027. Waiting until early April to contact your plan is dangerously close, because the administrator needs processing time. Get the written notice in during January or February.

How a Timely Correction Is Taxed

When the excess is distributed by April 15, the tax treatment splits. The excess deferral amount itself is included in your gross income for the year you made the contribution, not the year you received it back. A 2026 excess distributed in March 2027 goes on your 2026 return.⁶ The earnings on that excess are taxed in the year they’re distributed, so they land on your 2027 return.⁴

Two protections apply to timely corrective distributions. The 10% early withdrawal penalty does not apply, even if you’re under 59½.⁴ And the excess isn’t taxed twice: you pay tax in the contribution year, and the distribution itself is not counted again because you already picked up the hit. You end up paying ordinary income tax once on the excess and once on the earnings. That’s it.

One thing you cannot do with a corrective distribution is roll it into an IRA or another retirement plan. The money must come to you directly.⁷

Roth 401(k) Excess Deferrals

Roth and pre-tax contributions share the same annual deferral limit. If your combined Roth and pre-tax deferrals exceed $24,500 (or your applicable catch-up ceiling), the excess must still be corrected by April 15. Because Roth contributions were already included in your taxable income when you made them, returning the excess Roth amount doesn’t create new tax on that portion. The earnings on the excess are taxable in the year distributed and don’t get the tax-free treatment that qualified Roth distributions normally enjoy.⁸

What Happens If You Miss April 15

This is where the real penalty kicks in. If the excess stays in the plan past April 15, you face double taxation. The excess was already included in your income for the contribution year, and the same money will be taxed again when you eventually take it out in retirement.⁵ On a $5,000 excess in a 24% bracket, that’s roughly $2,400 in extra federal tax you’ll eventually pay for no reason.

The uncorrected excess also loses any tax basis in the plan. After-tax money you contribute is normally tracked so you’re not taxed on it again when you withdraw. An uncorrected excess deferral is treated as if it were entirely pre-tax, and the plan assigns it zero basis.³ Every dollar comes out fully taxable at your ordinary rate.

The excess also becomes locked in the plan. Once April 15 passes, the money can only come out on a normal triggering event: you leave the job, retire, reach 59½, or hit another qualifying event.³ If that distribution happens before 59½, the 10% early withdrawal penalty applies on top of the double tax. There’s no special exemption for late corrective distributions the way there is for timely ones.

How Corrective Distributions Appear on Your Tax Forms

Your plan reports a corrective distribution on Form 1099-R. The distribution code in Box 7 tells you and the IRS which tax year the money belongs to. Code P means the excess deferral is taxable in the prior year. Code 8 means it’s taxable in the current year.⁹ In a typical correction where 2026 excess deferrals are distributed in early 2027, you’d see Code P on a 1099-R issued for 2027, meaning the excess deferral amount belongs on your 2026 return. The earnings portion, taxable in 2027, comes on a separate 1099-R with Code 8.

You need to include the excess deferral amount as income on your Form 1040 for the contribution year. If you’ve already filed that return before receiving the corrective distribution, you’ll likely need to amend it. The IRS won’t automatically adjust your return based on the 1099-R. When a Roth 401(k) is involved, the plan issues the corrective distribution on a separate 1099-R from any traditional account distributions.⁹

1
Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
2
Internal Revenue Service. COLA Increases for Dollar Limitations on Benefits and Contributions
3
eCFR. 26 CFR 1.402(g)-1 – Limitation on Exclusion for Elective Deferrals
4
Office of the Law Revision Counsel. 26 USC 402 – Taxability of Beneficiary of Employees Trust
5
Internal Revenue Service. Consequences to a Participant Who Makes Excess Deferrals to a 401(k) Plan
6
Internal Revenue Service. 401(k) Plan Fix-It Guide – Elective Deferrals Werent Limited to the Amounts Under IRC Section 402(g)
7
Internal Revenue Service. Fixing Common Plan Mistakes – Failure to Limit Contributions for a Participant
8
Internal Revenue Service. Retirement Plans FAQs on Designated Roth Accounts
9
Internal Revenue Service. 2025 Instructions for Forms 1099-R and 5498