HSA Excess Contributions: How to Fix the 6% Excise Tax Before It Compounds

An HSA excess contribution happens more easily than most employees expect, and it carries a real cost if nobody catches it in time. The IRS charges a 6% excise tax on the amount over the limit for every year it sits in the account, a penalty that keeps applying year after year until someone fixes it. This guide explains what counts as an excess contribution, why it usually happens, how to correct it before the deadline, and what role an employer actually has when the excess came through payroll.

What Counts as an HSA Excess Contribution?

An HSA excess contribution is any amount contributed to a health savings account, from any source combined, that goes over the IRS annual limit for that person's coverage tier. For 2026, the limit is $4,400 for self-only HDHP coverage and $8,750 for family HDHP coverage, per IRS Revenue Procedure 2025-19, plus a $1,000 catch-up contribution for anyone 55 or older by the end of the year.

The limit counts every dollar together. Employer contributions, payroll pre-tax elections through a Section 125 plan, and any after-tax deposit the employee makes directly to the HSA custodian all count toward the same annual ceiling. An employee who receives a $1,000 employer seed contribution and also elects $4,000 through payroll has used $5,000 of their 2026 self-only limit, leaving $600 in additional room before hitting the excess threshold, not the full $4,400.

What Is the 6% Excise Tax on Excess HSA Contributions?

The 6% excise tax under IRC Section 4973 applies to any excess HSA contribution that remains in the account at the end of the tax year, and it applies again every following year the excess stays uncorrected. The tax is calculated on the lesser of the excess contribution amount or the fair market value of the HSA at year-end, so a small account balance can cap the tax even if the original excess was larger.

This is not a one-time penalty. An employee who over-contributes by $2,000 in 2026 and does not correct it owes 6% of that amount, $120, for 2026. If the excess is still sitting in the account at the end of 2027, the employee owes another 6% that year too, and the cycle repeats until the excess is either withdrawn or absorbed by contributing less than the limit in a future year.

What Causes Most HSA Excess Contributions?

Most excess contributions trace back to a mid-year change that nobody adjusted the payroll election for. The most common causes are:

• A mid-year coverage change. An employee who switches from family HDHP coverage to self-only coverage partway through the year, often after a divorce or a dependent aging off the plan, keeps contributing at the higher family-coverage rate through payroll unless the election is manually reduced.
• Both spouses contributing to family coverage. When both spouses have their own HSA under one family HDHP, the $8,750 family limit is shared between the two accounts. Each spouse contributing as if they had their own separate $8,750 limit creates an excess almost immediately.
• Combining outside contributions with payroll elections. An employee who makes a personal HSA contribution directly to the custodian in addition to their payroll election, without checking the running total, is a routine cause of excess contributions that has nothing to do with the employer's payroll system.
• Employer contribution errors. A payroll system that does not net an employer's seed or match contribution against the employee's own payroll election allows the combined total to exceed the annual limit without either side noticing.
• Becoming HSA-ineligible mid-year. Enrolling in Medicare, in most cases, ends HSA eligibility the month coverage starts, and any contribution made for a month of Medicare eligibility becomes an excess contribution even if the annual dollar limit was never reached.

How Does the Medicare Enrollment Trap Create Excess Contributions?

Medicare enrollment is one of the least understood causes of an HSA excess contribution, and it catches employees who are still actively working past 65. Enrolling in Medicare Part A makes a person ineligible to contribute to an HSA starting the month that Medicare coverage begins, under IRS Publication 969.

The trap is timing. An employee who files for Social Security retirement benefits after turning 65 can trigger Medicare Part A enrollment retroactive up to six months, per the Centers for Medicare and Medicaid Services, but never earlier than the month the person turned 65. An employee who keeps contributing to their HSA through payroll during those retroactive months, unaware that filing for Social Security just made them Medicare-eligible for that period, ends up with an excess contribution for every one of those months, discovered only when the HSA custodian or the employee's tax preparer catches the mismatch the following spring.

How Do You Correct an HSA Excess Contribution Before the Tax Deadline?

The cleanest fix is a corrective distribution. Withdrawing the excess contribution and any earnings it generated before the tax filing deadline for that year, including extensions, generally around October 15 of the following year for someone who files an extension, avoids the 6% excise tax entirely for that year. The withdrawn principal is not taxed again, since it was either after-tax money to begin with or already added back to W-2 wages, but the earnings portion is reported as taxable income for the year the excess contribution was made.

The HSA custodian handles the mechanics of a corrective distribution, not the employer or the IRS directly. An employee requests the correction from whichever bank or financial institution holds the HSA, specifying that it is a withdrawal of excess contributions, so the custodian codes the distribution correctly on Form 1099-SA rather than treating it as an ordinary, potentially taxable withdrawal.

What Happens If You Miss the Correction Deadline?

An employee who does not withdraw the excess by the tax filing deadline owes the 6% excise tax for that year, reported on IRS Form 5329, and the excess stays subject to the same 6% tax every year afterward until it is resolved. There are still two ways to resolve it after the deadline has passed.

The first is a late corrective distribution. Withdrawing the excess in a later year still stops the excise tax from applying to future years, even though the tax already owed for prior years does not go away. The second is to simply under-contribute in a future year, since the IRS allows an employee to apply a prior excess against a later year's unused contribution room instead of taking a distribution, effectively absorbing the excess by contributing less than the annual limit the following year. Either path requires filing Form 5329 to report the correction.

Can an Employer Fix an Excess Contribution Made Through Payroll?

It depends entirely on timing. If an employer's payroll system creates an excess contribution and the error is caught within the same calendar year, before W-2s are prepared, the employer can generally correct it directly with the HSA custodian and adjust the employee's payroll records, including Box 1, Box 3, Box 5, and the Box 12 Code W amount on Form W-2, so the excess never shows up on the filed return at all.

Once the calendar year has closed and a W-2 has already been issued, the IRS generally does not allow an employer to simply pull money back out of an employee's HSA, under guidance in IRS Notice 2008-59. At that point, correcting the excess becomes the employee's responsibility, worked out directly with the HSA custodian through a corrective distribution and reported on the employee's own Form 8889 and, if the deadline has passed, Form 5329. An employer's best tool for preventing this situation is a payroll system that caps HSA elections at the correct annual limit and flags a mid-year coverage change the same pay period it happens, which is exactly the kind of setup <a href="/blog/section-125-cafeteria-plan-2026-guide">a properly administered Section 125 plan</a> is built to catch. <a href="/blog/maximizing-fica-tax-savings">See the full FICA savings math for pre-tax benefits</a> for how HSA payroll elections fit into the broader Section 125 savings picture.

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Frequently Asked Questions

Sources: Internal Revenue Service Publication 969, IRS Revenue Procedure 2025-19, IRC Section 4973, IRS Form 5329 instructions, IRS Notice 2008-59, and Centers for Medicare and Medicaid Services guidance on Medicare Part A retroactive enrollment.