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Tax treatment, contribution limits, and the right order to fill them
Three types of accounts hold most Americans' retirement savings — the traditional 401(k), the Roth IRA, and the Health Savings Account. Each taxes your money differently: one taxes you now, one taxes you later, and one (the HSA) might not tax you at all. Knowing which to fill first — and how much — is one of the highest-leverage financial decisions you can make.
Get the order right and you shave years off your timeline. Get it wrong and you pay tens of thousands more in taxes over your lifetime — not because you invested in the wrong things, but because you put them in the wrong containers.
The key difference is when you pay tax: traditional accounts defer taxes to withdrawal, Roth accounts pay taxes upfront and let growth compound tax-free, and HSAs avoid taxes at every step when used for medical expenses.
| Feature | Traditional 401(k) | Roth IRA | HSA |
|---|---|---|---|
| 2025 contribution limit | $23,500 ($31,000 if 50+) | $7,000 ($8,000 if 50+) | $4,300 single / $8,550 family |
| Tax on contribution | Pre-tax — reduces taxable income now | After-tax — no deduction | Pre-tax — reduces taxable income now |
| Tax on growth | Tax-deferred | Tax-free | Tax-free |
| Tax on withdrawal | Ordinary income tax | Tax-free (after 59½ + 5yr rule) | Tax-free for medical |
| RMDs at 73 | Yes | No | No |
| Early withdrawal penalty | 10% before 59½ | 10% on earnings only (principal is free) | 20% for non-medical before 65 |
| Income limit | None (employer plan) | Phases out ~$150K–$165K single, ~$236K–$246K MFJ | Must have qualifying HDHP |
Every other tax-advantaged account has two advantages — either a deduction plus tax-deferred growth, or after-tax contributions plus tax-free growth. The HSA is the only account that can deliver all three: pre-tax contributions, tax-free growth, and tax-free withdrawals.
1. Contributions are pre-tax
HSA contributions reduce your taxable income dollar-for-dollar, just like a traditional 401(k). If you contribute $4,300 and you're in the 22% bracket, that's $946 in immediate tax savings — before your money has earned a single dollar of return.
2. Growth is tax-free
HSA balances can be invested in index funds and grow without any capital gains tax, dividends tax, or year-end distributions. Over 20 years, a maxed HSA can grow to $200,000+ in a total market index fund — all of it tax-free.
3. Withdrawals are tax-free for medical
Any qualified medical expense — doctor visits, prescriptions, dental, vision, Medicare premiums after 65 — can be reimbursed from an HSA tax-free. After 65, non-medical withdrawals are simply taxed as ordinary income, like a traditional IRA, with no additional penalty.
The FIRE strategy: receipt arbitrage
There is no time limit on HSA reimbursements. Pay medical bills out of pocket today, save every receipt, and reimburse yourself from the HSA 10 or 20 years later — after the HSA balance has compounded tax-free. A $200 doctor visit today, left to grow at 7% real for 20 years, becomes $774. You receive $774 tax-free in retirement for a medical expense you already paid.
The order matters because each account type has different tax treatment, and filling them in the wrong sequence leaves money on the table. This is the consensus priority order from decades of personal finance research:
Employer 401(k) match
Always capture the full employer match first, no exceptions. A 50% or 100% employer match is an instant guaranteed return that no investment can beat. Leaving this on the table is equivalent to turning down part of your salary.
HSA to max
If you have a high-deductible health plan (HDHP), the HSA is the single best account in the US tax code. The triple tax advantage — pre-tax contribution, tax-free growth, tax-free withdrawal for medical — is unmatched. Contribution limits for 2025: $4,300 single, $8,550 family.
Roth IRA to max
Especially powerful if you expect to be in a higher tax bracket in retirement, if you're young, or if you plan to retire early. Roth withdrawals don't count as income for ACA subsidy calculations and don't trigger Medicare IRMAA surcharges. 2025 limit: $7,000 ($8,000 if 50+). Phases out at higher incomes.
Traditional 401(k) to max
The pre-tax deduction is most valuable when your marginal rate is high — 22% or above. In early retirement, when your income drops, you can do Roth conversions at lower rates. 2025 limit: $23,500 ($31,000 if 50+).
Mega backdoor Roth
If your 401(k) plan allows after-tax contributions (beyond the standard $23,500), you can contribute up to the total limit (~$70,000 combined in 2025) and convert those after-tax dollars to Roth in-plan or via rollover. Not all employers offer this — check your plan documents.
Taxable brokerage
No contribution limit and no withdrawal restrictions. You'll owe capital gains tax on gains, but long-term capital gains rates (0%, 15%, or 20%) are often much lower than ordinary income rates. Essential for FIRE savers who need access to funds before 59½ without penalties.
These priorities assume you're working toward FIRE and have flexibility in your income. If you're above the Roth IRA income limit, use the backdoor Roth strategy — contribute to a non-deductible traditional IRA, then immediately convert to Roth.
The decision between Roth and traditional contributions is fundamentally a tax rate arbitrage question: are your taxes higher now or in retirement? Get this right and you can save tens of thousands in taxes over a working lifetime.
| Your situation | Best choice | Reasoning |
|---|---|---|
| Young / low income now | Roth | You're paying taxes at today's lower rate. Tax-free compounding over decades is extremely valuable when you have time. |
| High income now (22%+ bracket) | Traditional | The deduction saves you at 22-37% now. In retirement you'll likely withdraw at 12-22%, capturing the spread. |
| Early retiree, pre-Medicare | Roth critical | Roth withdrawals don't count as MAGI for ACA premium subsidies. Every dollar of traditional withdrawal may cost you hundreds in lost subsidies. |
| High earner building toward FIRE | Traditional now → Roth ladder in retirement | Maximize deduction during high-earning years. In low-income early retirement, convert traditional to Roth annually at low marginal rates. |
The Roth conversion ladder for early retirees
Many FIRE savers use traditional 401(k) during high-earning years (capturing the 22-37% deduction), then retire early and spend low-income years doing Roth conversions in the 0-12% brackets. After five years, those converted dollars can be withdrawn tax-free. This is the most tax-efficient path for most high-income FIRE savers — but it requires careful planning to ensure you have enough accessible funds during the five-year conversion window.