Retirement Accounts: 401k and IRA Explained

The most expensive financial mistake most people make in their 20s isn't buying too much or saving too little. It's not understanding what the employer match actually is.

Millions of people contribute less than the full employer match to their 401k every year, which means they're leaving a guaranteed 50 to 100 percent return on the table. No investment strategy in the world produces that return reliably. The match does it before the market opens on Monday. The people who don't take it in full usually don't do so because nobody ever explained what it was in terms that made its value obvious.

Retirement accounts are worth understanding not because they're complicated — they're not — but because the decisions you make about them in your 20s and 30s have a larger impact on your financial situation at retirement than almost any other single decision you'll make. The math rewards people who start early in ways that are hard to catch up to later.

What the employer match actually is

A common match structure is 100% of your contributions up to 4% of your salary. If you make $60,000 a year and contribute 4% ($2,400), your employer contributes another $2,400. That's an immediate 100% return on that $2,400 before it's been invested for a single day. If you contribute 2% instead of 4%, your employer contributes 2% — and you've left $1,200 of free money on the table every year.

Match structures vary by employer. Some match 50 cents on the dollar up to 6%. Some have vesting schedules — the matched money becomes fully yours only after you've stayed for a certain number of years. Read your plan documents for the specific terms. But the general principle holds across almost every employer plan: not contributing enough to capture the full match is a specific, calculable dollar loss every pay period.

What a 401k actually is

A 401k is not an investment. It's a tax-advantaged wrapper around investments. When you contribute to a traditional 401k, the money comes out of your paycheck before income taxes are applied — so a $500 contribution actually only reduces your take-home pay by $350 to $400 depending on your tax bracket. The money then goes into whichever investments you select inside the account and grows tax-deferred until you withdraw it in retirement.

Withdrawals in retirement are taxed as ordinary income. The bet you're making with a traditional 401k is that your tax rate in retirement will be lower than your tax rate now — which is true for most people, since retirees typically have lower income than they did during their working years.

The 2025 contribution limit for a 401k is $23,500 per year for people under 50. Most people can't max this out right away, and that's fine. The priority is the match first. Additional contributions beyond the match are valuable but secondary.

The IRA — and why it exists alongside a 401k

An IRA — Individual Retirement Account — is a retirement account you open yourself, independent of any employer. The 2025 contribution limit is $7,000 per year for people under 50. IRAs have two main variants: traditional and Roth. The distinction between them is about when you pay taxes, which is the same distinction as with the 401k.

The reason to have an IRA alongside a 401k is investment flexibility. 401k plans offer whatever investment options the employer has negotiated with the plan provider — sometimes good, sometimes limited and expensive. An IRA at a brokerage like Fidelity, Vanguard, or Schwab gives you access to any investment available on that platform, including low-cost index funds with expense ratios a fraction of what some 401k funds charge.

Roth vs. traditional — the question that determines which is right

A Roth account — whether a Roth IRA or a Roth 401k — is funded with after-tax money. You don't get the upfront tax deduction. In exchange, the money grows tax-free, and qualified withdrawals in retirement come out with no tax owed at all. A traditional account gives you the tax deduction now but taxes the withdrawals later.

The one question that determines which is better: is your tax rate higher now or will it be higher in retirement? If you're in your 20s or early 30s and earning a relatively modest income, your tax rate is probably near the lowest it will be in your career. Paying tax now (Roth) and getting tax-free growth for forty years is usually the better deal. If you're in peak earning years and in a high bracket, deferring the tax with a traditional account is often the right call.

The Roth IRA has one additional advantage: contributions (not earnings) can be withdrawn at any time without penalty. This makes it function as a somewhat flexible account — the contributions are accessible in a genuine emergency, though the growth is not. That flexibility is why financial planners often recommend the Roth IRA specifically for people in their 20s and early 30s who are still building an emergency fund.

What to invest in once you're inside the account

The account is just the container. What matters is what goes inside. Most people opening a retirement account for the first time make one of two mistakes: they leave the money in the default cash position (which earns almost nothing), or they try to pick individual stocks inside the account and make the same mistakes they'd make in a taxable brokerage.

The simplest correct answer for most people is a target-date fund corresponding to the year you expect to retire. A target-date 2055 fund for someone planning to retire around 2055 automatically holds a diversified mix of stocks and bonds, adjusts the allocation to become more conservative as the target date approaches, and rebalances itself. The expense ratios at major providers (Fidelity, Vanguard, Schwab) run 0.10% to 0.15% annually — essentially nothing.

The alternative to target-date funds is building your own allocation from low-cost index funds: a total U.S. stock market fund, a total international fund, a bond fund. This gives you slightly more control over the allocation and marginally lower fees in some cases. For most people starting out, the difference is negligible, and the target-date fund is the better choice because it requires no ongoing decisions.

The order that makes sense

The contribution order that most financial planners agree on: first, contribute to your 401k up to the full employer match. Then, contribute to a Roth IRA up to the annual limit ($7,000 in 2025 for people under 50). Then, if you have more to invest, go back to the 401k and contribute beyond the match up to the annual limit. After that, taxable brokerage accounts.

The Roth IRA comes before the additional 401k contributions in this order because of the investment flexibility and the tax-free growth. The 401k beyond the match is still valuable — the tax deferral is real — but the Roth IRA's combination of flexibility, tax-free growth, and broad investment access makes it the priority for most people who have the match covered.

Starting at 25 vs. 35 — the math people underestimate

Contributing $500 a month to a retirement account starting at age 25, with a 7% average annual return, produces roughly $1.3 million by age 65. Contributing the same $500 a month starting at 35 produces roughly $610,000 by age 65 — less than half. The ten-year gap in starting age costs over $700,000 in ending balance from identical monthly contributions.

The reason is compounding. The first ten years of contributions grow for an additional ten years at the end. Money contributed at 25 has 40 years to compound. Money contributed at 35 has 30 years. The difference in ending value is nonlinear — each additional year of compounding amplifies all the years before it.

This is not an argument for perfection at 25. Contributing $100 a month at 25 while paying off debt is still meaningfully better than contributing $0. The compounding clock starts whenever you start. What it doesn't do is run backwards — the years you wait are years the clock isn't running, and they compound into a gap that's genuinely difficult to close with larger contributions later.

The match is free money. The Roth is the best tax deal most people will ever have access to. The time is the thing that can't be bought back.