401(k) vs Roth IRA: Which Should You Fund First?

A 401(k) and a Roth IRA are not rivals. They are two different tax wrappers around the same investments, and almost every US saver should eventually use both. The question that actually matters is order: which dollar goes where first. Get the order right and the difference over a 30-year career is routinely six figures, not because the investments differ, but because of the employer match and the tax bracket you pay at.

The one-minute answer

• Fund the 401(k) up to the full employer match.
• Then fund a Roth IRA to the annual limit.
• Then go back and fill the rest of the 401(k).
• Then use a taxable brokerage account, an HSA, or both.

That order changes in exactly two situations: your employer offers no match (start with the Roth IRA), or your marginal tax rate today is unusually high compared with the rate you expect in retirement (favour pre-tax 401(k) dollars sooner).

Step 1 — the match is a guaranteed return

A typical match is 50% of the first 6% of salary, or dollar-for-dollar on the first 3–4%. On a $80,000 salary, a 50%-of-6% match is $2,400 a year of free money for contributing $4,800. No investment you can buy offers a guaranteed 50% first-year return. Missing the match is the single most expensive mistake in US retirement saving, and it is completely reversible this month by raising your contribution percentage in your payroll portal.

Worked example: contribute the match for 30 years at a 7% average return and that $2,400/year of employer money alone grows to roughly $227,000. That is the money most people leave on the table.

Step 2 — why the Roth IRA usually comes next

A Roth IRA is funded with after-tax dollars, grows tax-free, and is withdrawn tax-free after age 59½ (assuming the account is at least five years old). Three features make it worth prioritising over extra 401(k) dollars:

• Tax-free compounding. $7,000 a year for 30 years at 7% becomes about $708,000 — and none of it is taxed on the way out.
• Investment choice. An IRA at any major broker gives you the whole market; most 401(k) menus give you 15–25 funds, sometimes with higher expense ratios.
• Contribution flexibility. Your own contributions (not the earnings) can be withdrawn at any time, penalty-free. That makes a Roth IRA a genuine backstop in a way a 401(k) is not.

Step 3 — then max the 401(k)

Once the Roth IRA is full, extra 401(k) dollars are still excellent: the contribution limit is far higher than an IRA's, contributions come straight off your taxable income, and payroll deduction makes it automatic. If your plan offers a Roth 401(k) option, you can even split contributions between pre-tax and Roth buckets inside the same plan.

Pre-tax vs Roth: the actual trade-off

Pre-tax contributions cut your tax bill today at your marginal rate. Roth contributions cut your tax bill in retirement at your future rate. If your marginal rate today is higher than your expected retirement rate, pre-tax wins. If it is lower — early career, a gap year, a low-income year, or you expect large retirement balances — Roth wins.

Worked comparison: $10,000 contributed at a 24% marginal rate. Pre-tax saves $2,400 now and the full $10,000 compounds, but every future withdrawal is taxed as ordinary income. Roth costs $2,400 now, but a $10,000 contribution growing to $76,000 over 30 years comes out entirely tax-free. Same investments, very different end-of-life tax bills.

The tax-bucket strategy nobody explains

Retirement is easier when you hold three buckets: pre-tax (401(k)), tax-free (Roth), and taxable (brokerage). With all three you can choose each year how much taxable income to realise — staying under an IRS bracket edge, an IRMAA Medicare surcharge threshold, or an ACA subsidy cliff. Savers with only pre-tax money have no such control: every dollar they spend is taxable income.

Rules and limits to know

• Required minimum distributions. Traditional 401(k)s and IRAs require withdrawals in later retirement; Roth IRAs do not for the original owner.
• Income limits. Roth IRA direct contributions phase out at higher incomes. Above the limit, the backdoor Roth (non-deductible IRA contribution converted to Roth) is the standard workaround — clean if you hold no other pre-tax IRA balances, because of the pro-rata rule.
• Five-year rule. Roth earnings are tax-free only after the account has been open five years and you are 59½ or older.
• Vesting. Employer match money may vest over 2–6 years. Leaving early can forfeit unvested dollars — worth checking before you resign.

Pro tips that compound

• Turn on auto-escalation: +1% contribution every year. You will not feel it, and it roughly doubles most people's lifetime contribution rate.
• Fund the Roth IRA in January rather than December — a full extra year in the market, every year.
• Roll old 401(k)s into either your current plan or an IRA so you can actually see and manage the allocation.
• Keep the total stock/bond split consistent across all accounts rather than balancing each one separately.

Frequently asked questions

What if my employer doesn't match? Start with the Roth IRA, then the 401(k). The match is the only reason to fund the 401(k) first.

Can I contribute to both in the same year? Yes. They have separate limits, and using both is normal.

Is a Roth 401(k) the same as a Roth IRA? Similar tax treatment, different account. The Roth 401(k) has a much higher contribution limit and payroll convenience; the Roth IRA has better investment choice and easier access to contributions.

What if I need the money before retirement? Roth IRA contributions come out any time, penalty-free. 401(k) money generally does not — assume it is locked until 59½.

Should I stop contributing to pay off debt? Keep the match, always. Above the match, anything costing more than roughly 7–8% interest is usually worth clearing first.

Run the numbers on your own salary, match and time horizon before you trust a rule of thumb — the retirement calculator linked above does it in under two minutes.