What Happens If You Overcontribute to Your HSA?

An HSA overcontribution triggers a 6% IRS excise tax on the excess amount, and that penalty repeats every year the extra money stays in the account. You can avoid it by asking your HSA custodian to return the excess (along with any earnings it produced) before your tax filing deadline, including extensions. If you miss that window, you can still stop the bleeding by undercontributing in a later year to absorb the excess, though the 6% applies for each year-end the excess is still sitting there.

The 6% Excise Tax, and Why It Compounds

The core penalty is a 6% excise tax on the excess amount in your HSA at the end of the tax year.¹ It isn’t a one-time hit. The IRS charges the 6% again every year the excess stays put. A $1,000 overcontribution left alone for five years costs $300 in excise tax alone, on top of losing the deduction.

The excess amount is also included in your gross income, so you pay ordinary income tax on the same dollars you’re being penalized for. You calculate the excise tax on Form 5329, Part VII, and attach it to your Form 1040.²

2026 Contribution Limits

Before deciding you overcontributed, confirm the ceiling. For 2026:

Self-only HDHP coverage: $4,400
Family HDHP coverage: $8,750
Catch-up if you’re 55 or older: an additional $1,000

Someone 55 or older with self-only coverage can contribute up to $5,400, and someone with family coverage up to $9,750.³ The $1,000 catch-up is fixed by statute and doesn’t adjust for inflation.⁴ If both spouses are 55 or older, each catch-up must go into that spouse’s own HSA. You cannot double up in one account.

These limits count every dollar going in from every source: your contributions, your employer’s, and anyone else’s. Forgetting to add the employer’s share is one of the most common ways people slip over.

How People End Up Over

Most excess contributions are accidents from timing gaps, coverage changes, or arithmetic that didn’t catch up with reality.

Mid-Year Coverage Changes

If you had HDHP coverage for only part of the year, your limit is prorated at 1/12 of the annual amount for each month you had qualifying coverage on the first day. Six months of self-only coverage in 2026 gives you a $2,200 limit, not $4,400.³ Payroll deductions that keep running at the full-year rate after a plan change are a common source of quiet overcontribution.

Double-Counting Employer Contributions

Employer contributions count toward your limit. A $1,200 employer deposit plus $3,500 of your own money under self-only coverage puts you at $4,700, which is $300 over. Errors happen most often when you change jobs mid-year or switch between self-only and family coverage.

Spouse Catch-Up Mistakes

Each spouse’s $1,000 catch-up has to sit in that spouse’s own HSA. Dropping both catch-ups into one account creates a $1,000 excess in that account, even though the couple was entitled to the money as a whole.

Fix It Before the Deadline: Withdraw the Excess

The cleanest fix is to call your HSA custodian and request a return of excess contribution before your tax filing deadline, including extensions. For a 2026 excess, that’s typically April 15, 2027, or October 15, 2027 with an extension.

You can’t just pull out the extra principal. The custodian also calculates and removes the net income attributable (NIA) to that money, meaning the gains or losses the excess earned while it sat in the account. If the account lost value, the NIA can be negative, and you’ll take out slightly less than you put in.

The tax treatment splits in two:

The excess principal is included in your gross income for the year the contribution was made. A 2026 excess is 2026 income no matter when you actually pull it out.
The NIA is ordinary income in the year you receive the distribution. Pulling a 2026 excess out in early 2027 means the earnings show up on your 2027 return.⁵

Meet the deadline and you avoid the 6% excise tax for that year entirely. The custodian reports the withdrawal on Form 1099-SA with distribution code 2, which flags it as a return of excess rather than a regular distribution.⁶

Fix It After the Deadline: Absorb It in a Future Year

If the deadline is gone and the money is stuck, you have another option. Undercontribute in a later year and let the shortfall absorb the earlier excess. The IRS lets you apply prior-year excess contributions still sitting in your HSA, up to the smaller of your unused current-year limit or the excess balance at the start of the year.⁷

The catch: you still owe 6% for every year the excess is in the account at year-end. Overcontribute by $2,000 in 2026, contribute $2,000 less than the limit in 2027, and you pay $120 for 2026 but nothing for 2027 onward. This route makes sense for small amounts where the penalty is tolerable and the withdrawal paperwork isn’t worth the trouble.

Two Special Traps

The Last-Month Rule Testing Period

The last-month rule lets you contribute the full annual amount if you had HDHP coverage on December 1, treating you as eligible all year.⁴ The price is a testing period: you must stay in an HDHP through December 31 of the following year. Used the rule for 2026? You need HDHP coverage through December 31, 2027.⁷

Fail the testing period and the contributions that only qualified through the last-month rule get added back to your income, plus a 10% additional tax on that amount, reported in Part III of Form 8889.⁸ The only exceptions are loss of eligibility due to death or disability. This penalty is separate from the 6% excise tax and can stack with it if your situation also creates an excess under the regular rules.

People typically trip this by switching to a non-HDHP plan at open enrollment or starting a new job with traditional insurance. If you’re not sure you’ll keep the HDHP through the testing period, sticking to the prorated amount is safer.

Medicare Backdating

Medicare creates a particularly ugly version of overcontribution. Once any part of Medicare is effective, your HSA limit drops to zero, even if you still have HDHP coverage through work. Medicare Part A can be backdated up to six months when you enroll after age 65, which can retroactively turn months of legitimate-looking contributions into excess.

Say you turned 65 in March 2026, kept working with HDHP coverage, contributed through September, and then enrolled in Medicare Part A in October with an April effective date. Every contribution from April through September, yours and the employer’s, is now excess. The fix is the same return-of-excess process, with the same deadline to avoid the 6%.⁷ If you’re approaching 65 and plan to delay Medicare, stop HSA contributions at least six months before your expected Medicare start date so the backdating can’t reach them.

When Your Employer Put in Too Much

You, not your employer, are the one who owes the excise tax to the IRS. The correction path depends on who caused the error.

If the mistake was administrative or a payroll processing error, the employer can ask the HSA custodian to return the mistaken contribution directly to the employer. The IRS recognizes examples like duplicate payroll files, decimal-point errors, and amounts that don’t match the employee’s salary reduction election. Ideally this happens before the end of the calendar year.

If the employer won’t reverse it, you can contact the custodian yourself and request a return of excess. It will be processed as your withdrawal and reported on a Form 1099-SA with distribution code 2. Employer contributions appear in Box 12 of your W-2 with code W, and any excess employer contribution not corrected by the employer has to be included in your gross income.⁷

The Forms Involved

Every HSA owner files Form 8889 to reconcile contributions against the annual limit. Part III of that form is where you handle a failed last-month-rule testing period, including the 10% additional tax.⁹

Form 5329, Part VII, is where the 6% excise tax on HSA excess contributions is calculated. If you withdrew the excess by the deadline, you don’t owe this tax and generally won’t need that part.¹⁰

Form 1099-SA from your custodian reports any corrective distribution, with distribution code 2 identifying it as a return of excess.⁵ The earnings portion (NIA) shown on that form goes on your Form 1040 for the year you received the distribution. If your employer put in too much and it wasn’t included in Box 1 of your W-2, you report the excess as other income on your Form 1040 yourself.⁷

1
Office of the Law Revision Counsel. 26 USC 4973 – Tax on Excess Contributions to Certain Tax-Favored Accounts
2
Internal Revenue Service. Form 5329 – Additional Taxes on Qualified Plans (Including IRAs) and Other Tax-Favored Accounts
3
Internal Revenue Service. Revenue Procedure 2025-19
4
Office of the Law Revision Counsel. 26 USC 223 – Health Savings Accounts
5
Internal Revenue Service. Form 1099-SA – Distributions From an HSA, Archer MSA, or Medicare Advantage MSA
6
Internal Revenue Service. Instructions for Forms 1099-SA and 5498-SA
7
Internal Revenue Service. Publication 969 – Health Savings Accounts and Other Tax-Favored Health Plans
8
Internal Revenue Service. Instructions for Form 8889
9
Internal Revenue Service. Instructions for Form 8889
10
Internal Revenue Service. Instructions for Form 5329