How Much Should I Contribute to My HSA Per Paycheck?

Your benefits portal wants a per-paycheck number, and the only figure it gives you to work with is an annual maximum that is not actually your maximum.

Four numbers produce the right answer. Here they are, worked all the way through for a family of four, with the three traps that catch people marked as you go.

The Four Numbers

  1. The IRS limit for your coverage tier and plan year.
  2. The catch-up, if you are 55 or older at any point during the year.
  3. Everything your employer puts in — seed, match, wellness credit, all of it.
  4. Your number of pay periods.

For a family choosing 2027 coverage, with an employer that seeds $750, paid every two weeks:
IRS family limit, 2027 $9,000
Catch-up (under 55) $0
Maximum into the account $9,000
Less employer contribution −$750
The most you may contribute $8,250
÷ 26 pay periods
Per paycheck $317.31

That is the whole calculation. The step that goes wrong is the subtraction.

The limits, both years

2026 2027
HSA limit — self-only $4,400 $4,500
HSA limit — family $8,750 $9,000
Catch-up, age 55+ $1,000 $1,000
HDHP minimum deductible — self-only $1,700 $1,750
HDHP minimum deductible — family $3,400 $3,500
HDHP maximum out-of-pocket — self-only $8,500 $8,700
HDHP maximum out-of-pocket — family $17,000 $17,400

Source: IRS Rev. Proc. 2025-19 for 2026 and Rev. Proc. 2026-24 for 2027. The catch-up is fixed in statute at $1,000 and is not indexed to inflation.

Use the limit for the plan year the coverage applies to, not the year you are enrolling in. Choosing in November 2026 for coverage starting 1 January 2027 means the 2027 limit.

Trap One: Employer Money Counts Against the Limit

The IRS limit caps what goes into the account, not what you personally put in. Employer contributions are not a bonus on top.

A family whose employer seeds $750 and who elects the full $9,000 themselves has put $9,750 into the account. The $750 excess is included in income and charged a 6% excise tax — and it keeps being charged 6% every year it stays there, which is how a single form-filling slip in November becomes an annual tax bill.

Ask HR for the exact annual employer figure, including anything conditional. A wellness credit that lands in the HSA if you complete a health assessment is an employer contribution, and it counts.

Trap Two: Part-Year Eligibility Is Prorated in a Specific Order

Eligibility is tested on the first day of each month. Start an HSA-eligible plan on 1 July and you are eligible for six months.

The IRS prorates the annual limit by those months, and employer money comes off the prorated figure:

Correct
Annual family limit $9,000
× 6/12 months eligible $4,500
Less employer contribution −$750
Your room $3,750

Do it the other way round — subtract first, then prorate — and you get $4,125, which is $375 too much. That $375 is an excess contribution, taxable and subject to the 6% charge, and nobody notices until a tax form disagrees with them.

There is an exception, and it is a trap of its own. The last-month rule lets you contribute the full annual amount if you are eligible on 1 December — but you must then stay eligible for the whole of the following year. Break that and the extra becomes taxable income plus a 10% penalty. It is a genuine option; it is not free.

Trap Three: You Cannot Fund an HSA and a General-Purpose Health FSA

Not in the same year, not as a couple where one spouse has the FSA. A general-purpose Health FSA makes you ineligible to contribute to an HSA, because it is itself a form of first-dollar health coverage.

If you are moving to an HSA-eligible plan, your Health FSA has to become a limited-purpose one — dental and vision only — or come off entirely. Check your spouse’s election too; theirs disqualifies you just as effectively as your own.

What It Actually Costs You

This is the part worth sitting with, because the sticker figure overstates the pain considerably.

Payroll HSA deductions avoid federal income tax, state income tax where you have it, and FICA. At 22% federal, 5% state and 7.65% FICA — a combined marginal rate of 34.65%:

Your election Per paycheck (26) Tax and FICA saved Real cost to take-home
$2,000 $76.92 $693 $1,307
$4,000 $153.85 $1,386 $2,614
$8,250 (the full room) $317.31 $2,859 $5,391

Setting aside $4,000 costs about $2,614 of spendable income. That gap is the entire argument for the account.

One detail that matters more than it looks: the FICA saving only applies to payroll deductions. Fund an HSA yourself from a bank account and the contribution is still income-tax deductible, but you do not get the 7.65% back. Same money, roughly 7.65% worse — which is why routing it through payroll is worth the small hassle of getting the election right in November.

So What Number Should You Pick?

Work down this list and stop at the first one that binds.

1. At minimum, cover the gap the plan exposes you to. A $3,500 deductible means $3,500 of charges you pay in full. Funding that through the HSA rather than from your checking account makes it roughly a third cheaper. This is the floor, and for most households it is also the right answer.

2. If you can, fund the full room. Money in an HSA is the only account that is untaxed going in, untaxed while it grows, and untaxed coming out for medical costs. Nothing else in the tax code does all three. Left invested rather than sitting in cash, it behaves like a retirement account with a better exit.

3. Do not fund an HSA at the cost of an employer 401(k) match. A 50% or 100% match is a bigger and more certain return than the HSA’s tax treatment. Match first, then HSA, then the rest.

4. Remember you can change it. Unlike an FSA election, HSA contributions can usually be adjusted during the year through payroll. Setting $317.31 in November and dropping it in March because something else came up is allowed and costs you nothing. Electing an FSA amount and changing your mind is not.

And one thing that is genuinely optional: you do not have to spend it. Pay small medical costs from cash, keep the receipts, and let the account compound — the IRS puts no deadline on reimbursing yourself for a qualified expense, so a receipt from this year can be claimed a decade from now. That is a record-keeping commitment rather than a free lunch, but it is the version of the account that does the most work.

If your plan is not HSA-eligible, none of this applies and the parallel decision is a Health FSA — which account you get is decided by the plan you chose, not the other way round. And if you have not settled the plan yet, do that first: the account only exists because of the plan.

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Frequently Asked Questions

How do I work out my HSA contribution per paycheck?

Take the IRS limit for your coverage tier and plan year, add the $1,000 catch-up if you turn 55 or older during the year, subtract everything your employer contributes, then divide by your number of pay periods. For a family in 2027 the limit is $9,000; a $750 employer seed leaves $8,250 of room, which is $317.31 across 26 pay periods. The step people skip is the subtraction — employer money counts against the same limit.

Does my employer's HSA contribution count against my limit?

Yes. The IRS limit is a limit on everything that goes into the account, not on what you personally contribute. If the family limit is $9,000 and your employer puts in $750, you may contribute $8,250. Electing $9,000 yourself would put $9,750 into the account and create a $750 excess contribution, which is taxable and carries a 6% excise charge for every year it stays there.

What does an HSA contribution actually cost you in take-home pay?

Your contribution less the tax it avoids. Payroll HSA deductions escape federal income tax, state income tax where applicable, and FICA — so at 22% federal, 5% state and 7.65% FICA, a combined 34.65%, a $4,000 contribution reduces take-home pay by about $2,614. Funding an HSA yourself from a bank account instead is still income-tax deductible but does not escape FICA, which is worth roughly 7.65% less.

How is an HSA prorated if I am only eligible for part of the year?

The IRS prorates the annual limit by the number of months you are eligible on the first day of the month, and employer money counts against that prorated figure — not the other way round. Six months of family eligibility in 2027 gives $4,500 of room, and a $750 employer seed reduces it to $3,750. Prorating your own contribution instead of the limit is the common error, and it produces an excess contribution that is taxed every year until it is corrected.

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