You can increase your HSA contributions at any point in the year. HSAs aren’t like flexible spending accounts, where your election locks in at open enrollment. If your money goes in through payroll, you update the amount in your employer’s benefits or payroll system. If you contribute directly from a bank account, you send more whenever you want. The only real constraint is the annual IRS limit, and staying under it is your responsibility, not your employer’s.
Changing the Amount Through Payroll
Log into whichever benefits or payroll system your employer uses and find the HSA contribution section. Enter the new per-pay-period amount. Most systems show a projected annual total so you can check it against the limit before you submit. Save the confirmation.
Some employers still handle this on paper. In that case you fill out an HSA Contribution Change Form with your new per-period amount and an effective date, and send it to HR. The change typically starts with the next available payroll run. The form itself is short. The math is what matters.
Payroll contributions are the more tax-efficient route because the money goes in pre-tax, avoiding both income tax and FICA. That FICA savings is something you cannot recover any other way.
Adding Money Directly From a Bank Account
You can also push money into your HSA yourself. Log into your HSA provider’s site or app, choose the contribution option, and transfer funds from a linked bank account. You’ll need the external bank’s routing and account numbers if the accounts aren’t already linked. Transfers usually clear in two to three business days.
Direct contributions are useful for a year-end top-up to hit the limit, or for contributing to the prior tax year before the April deadline. The trade-off is that direct contributions only get you an income tax deduction when you file, and you don’t recapture the FICA savings that payroll contributions give you.
The Annual Limit You Have To Stay Under
For 2026, the IRS caps total HSA contributions at $4,400 for self-only HDHP coverage and $8,750 for family coverage. These are combined limits. Everything counts: your payroll contributions, your direct deposits, anything your employer puts in, and anything a family member deposits on your behalf.1Internal Revenue Service. Revenue Procedure 2025-19 – 2026 Inflation Adjusted Items for Health Savings Accounts
If you’re 55 or older by year-end and not enrolled in Medicare, you can add a $1,000 catch-up contribution on top. That raises the ceiling to $5,400 for self-only coverage and $9,750 for family coverage. The $1,000 catch-up is set by statute and doesn’t move with inflation.2Office of the Law Revision Counsel. 26 USC 223 Health Savings Accounts If both spouses are 55 or older, each can make the catch-up contribution, but each spouse needs a separate HSA to do so.
Subtract What Your Employer Is Putting In
Every dollar your employer deposits reduces the room you have left. If your employer contributes $2,000 and you have family coverage in 2026, your personal contribution ceiling drops from $8,750 to $6,750. Employer contributions made through a cafeteria plan or Section 125 arrangement count the same way.3Internal Revenue Service. HSA Contributions
Before you raise your payroll deduction, pull up your benefits portal or ask HR for the exact employer contribution amount for the year, including any match or seed deposit. This is the single most common way people end up over the limit.
Contributing for the Prior Tax Year
You have until April 15 of the following year to make HSA contributions that count toward the prior tax year. Contributions for 2025 can be made through April 15, 2026; contributions for 2026 can be made through April 15, 2027.4Internal Revenue Service. Publication 969 (2025), Health Savings Accounts and Other Tax-Favored Health Plans When you make one of these deposits, your HSA provider will ask which tax year it applies to. Get this designation right. If you leave it blank, the contribution usually defaults to the current year and can push you over the limit for two years in a row.
The Last-Month Rule If You Enrolled Mid-Year
Normally, if you picked up HDHP coverage partway through the year, your contribution limit is prorated by the number of months you were eligible. The last-month rule lets you skip the proration: if you’re an eligible individual on December 1, you’re treated as eligible for the full year and can contribute the full annual limit.4Internal Revenue Service. Publication 969 (2025), Health Savings Accounts and Other Tax-Favored Health Plans
The condition is the testing period. You have to stay in a qualifying HDHP from December 1 through December 31 of the following year. That’s 13 months. If you drop your HDHP during that stretch for any reason other than death or disability, the extra amount you contributed under the rule becomes taxable income, and you owe a 10% additional tax on top.4Internal Revenue Service. Publication 969 (2025), Health Savings Accounts and Other Tax-Favored Health Plans If there’s a real chance you’ll switch plans or enroll in Medicare inside that window, contribute the prorated amount instead.
Stop Before Medicare Starts
Once you enroll in any part of Medicare, your HSA contribution limit drops to zero for every month you’re covered. Money already in the account stays there and can still be spent tax-free on qualified medical expenses. You just can’t add to it.4Internal Revenue Service. Publication 969 (2025), Health Savings Accounts and Other Tax-Favored Health Plans
Watch out for the retroactive coverage rule. Medicare Part A can be backdated up to six months when you enroll. Any HSA contributions during that retroactive window become excess contributions and are subject to the 6% excise tax. If you’re approaching 65 and want to keep contributing, stop payroll deductions a few months before you plan to enroll to build in a buffer.
In the year you enroll, your limit is prorated by month. Turn 65 and enroll in July, and you get credit for six months of eligibility, including a prorated share of the $1,000 catch-up.
Fixing an Overcontribution
Excess HSA contributions trigger a 6% excise tax on the overage, and that tax repeats every year the excess sits in the account.5Office of the Law Revision Counsel. 26 USC 4973 Tax on Excess Contributions to Certain Tax-Favored Accounts On $500 of excess, that’s $30 a year. Small, but avoidable.
To fix it without the penalty, withdraw the excess plus any earnings it generated before your tax return due date, including extensions. You can’t deduct the withdrawn amount, and the earnings get reported as income in the year of the withdrawal.6Internal Revenue Service. Instructions for Form 8889 (2025)
If you already filed, you have another six months after the filing deadline (not counting extensions) to pull the excess out and file an amended return. Write “Filed pursuant to section 301.9100-2” at the top of the amended return and attach an explanation of the correction.6Internal Revenue Service. Instructions for Form 8889 (2025)