Can You Still Contribute to an HSA After Year End?

You can make a prior-year HSA contribution up until the federal tax filing deadline, which is April 15 for most filers. For the 2025 tax year, that means any deposit designated as a 2025 contribution has to clear your Health Savings Account by April 15, 2026.¹ That gives you roughly three and a half months after year end to look at your tax picture and top off the account before the window closes.

The Exact Cutoff Date

The deadline tracks the due date of your federal income tax return. When April 15 falls on a weekend or federal holiday, it shifts to the next business day. April 15, 2026, is a Wednesday, so 2025 contributions are due that day with no shift.

Filing an extension does not extend this deadline. Form 4868 pushes your return due date to October 15, but the HSA contribution window still closes on April 15.² Any money that lands in the account after April 15 automatically counts toward the current tax year.¹

ACH transfers usually take two or three business days to settle. If you wait until April 15 to click the button, the deposit may post after the deadline and lose its prior-year status. Start the transfer several business days early.

How Much You Can Still Contribute

Before making a deposit, figure out how much room you have left under the annual limit. The cap includes everything that went into the account for that tax year: your own deposits, payroll contributions through a cafeteria plan, and any employer contributions.

2025 limits: $4,300 for self-only HDHP coverage, $8,550 for family coverage.¹
2026 limits: $4,400 for self-only coverage, $8,750 for family coverage.³
Catch-up: If you were 55 or older by the end of the tax year, add an extra $1,000.¹

Your year-end HSA statement and your final pay stub will show what has already been contributed. Subtract that from the applicable cap to see what you can still put in.

Eligibility Runs Month by Month

Being an eligible individual is measured on the first day of each month. If you had qualifying HDHP coverage for only part of the year, your limit is generally prorated: eight months of self-only coverage means eight-twelfths of the annual cap.⁴ You also cannot be claimed as a dependent on someone else’s return, and you cannot be covered by disqualifying non-HDHP coverage, such as a spouse’s general-purpose flexible spending account.

There is one exception. If you were enrolled in a qualifying HDHP on December 1, the last-month rule lets you contribute the full annual amount as though you had HDHP coverage all year. The catch is a testing period that runs through December 31 of the following year. Drop your HDHP coverage during that window for any reason other than death or disability and the extra amount gets added back to your taxable income, plus a 10% additional tax.⁵

Medicare Shuts the Door

Once you are entitled to Medicare, your HSA contribution limit drops to zero starting with the first month of Medicare coverage.⁴ Part A enrollment after age 65 is backdated up to six months (but not before your 65th birthday), which turns any contributions made during those retroactive months into excess contributions. If you plan to keep contributing right up to Medicare enrollment, stop deposits at least six months before you sign up. Spending existing HSA funds on qualified medical expenses is still tax-free after enrollment; the restriction only applies to new contributions.

Designating the Deposit as a Prior-Year Contribution

This is the part people get wrong. Most HSA custodians default any incoming deposit to the current calendar year. To have your contribution counted for the prior year, you have to affirmatively mark it that way, usually through a dropdown or checkbox in the custodian’s online portal at the time you initiate the transfer. If you mail a check, include whatever designation form your custodian requires and note the tax year in the memo line.

Save the confirmation. If the custodian miscodes the deposit or the date comes into question, that receipt is what fixes it.

Employers can also make prior-year contributions up to the same April 15 deadline, including contributions run through a cafeteria plan.¹ If your employer front-loads its HSA contribution in January, check the designation before you assume that money belongs to the new year.

Reporting a Prior-Year Contribution on Your Return

Personal HSA contributions produce an above-the-line deduction, so you get the benefit whether or not you itemize. You claim it on Form 8889.

On Line 2, enter the total personal contributions you made for the tax year, including any deposits made between January 1 and April 15 of the following year that you designated as prior-year contributions. Do not include payroll contributions run through a cafeteria plan; those are reported as employer contributions elsewhere on the form. The deduction from Line 13 of Form 8889 carries to Schedule 1 (Form 1040), Part II, Line 13.⁵

Your custodian sends Form 5498-SA later in the year (typically by the end of May) showing total contributions received for the tax year.⁶ You do not attach it to your return, but hold on to it. If you already filed your return and then decide to make a last-minute prior-year deposit before April 15, you may need to amend the return to claim the additional deduction.

If You Contributed Too Much

Excess contributions carry a 6% excise tax on the extra amount, and that tax hits every year the excess stays in the account.⁷ Fixing it early is worth the trouble.

To avoid the excise tax entirely, withdraw the excess plus any earnings on it before your return due date, including extensions.⁵ This is the one HSA context where filing Form 4868 buys you more time; it gives you until October 15 to pull the excess out. Report the withdrawn earnings as income on your return for the year the excess contribution was made.

When you contact your custodian, ask specifically for a return of excess contribution. That phrase tells them to process the transaction under the correction rules rather than as a regular distribution. Common ways people end up here: switching from family to self-only coverage without adjusting payroll deductions, retroactive Medicare enrollment, and using the last-month rule and then losing HDHP eligibility.

A Word on State Taxes

Most states follow the federal treatment and allow the same HSA deduction on your state return. A few do not. California and New Jersey do not recognize HSA tax benefits at the state level, so contributions and any investment earnings inside the account are taxable on your state return even though the federal deduction still applies. Check your state’s rules before assuming the federal treatment carries over.

1
Internal Revenue Service. Publication 969 (2025), Health Savings Accounts and Other Tax-Favored Health Plans
2
Internal Revenue Service. Form 4868, Application for Automatic Extension of Time to File U.S. Individual Income Tax Return
3
Internal Revenue Service. Rev. Proc. 2025-19
4
Office of the Law Revision Counsel. 26 USC 223 – Health Savings Accounts
5
Internal Revenue Service. Instructions for Form 8889 (2025)
6
Internal Revenue Service. Form 5498-SA (Rev. December 2026) HSA, Archer MSA, or Medicare Advantage MSA Information
7
Office of the Law Revision Counsel. 26 USC 4973 – Tax on Excess Contributions to Certain Tax-Favored Accounts and Annuities