What Is a 401(k)? Retirement Savings Explained

A 401(k) is a retirement savings plan sponsored by your employer that lets you invest a portion of your paycheck before taxes are taken out. The money grows tax-deferred — you don't pay taxes on gains, dividends, or interest until you withdraw in retirement. And if your employer offers matching contributions, you're getting free money that multiplies your savings. It's the single most important wealth-building tool available to most working Americans.

How a 401(k) Works

You elect to contribute a percentage of your salary — say 10% — and that money is deducted from your paycheck before income tax is calculated. If you earn $80,000 and contribute 10%, only $72,000 is subject to income tax. The $8,000 contribution goes into your 401(k) account, where you choose from a menu of investment options (typically mutual funds and target-date funds).

Your investments grow without annual taxes on dividends, capital gains, or interest. When you withdraw the money in retirement (after age 59½), you pay ordinary income tax on the withdrawals. The idea: you're likely in a lower tax bracket in retirement than during your working years, so you pay less total tax over your lifetime.

The Employer Match

Many employers match a portion of your contributions — commonly 50% of the first 6% you contribute. If you earn $80,000 and contribute 6% ($4,800), your employer adds $2,400. That's an instant 50% return on your contribution — before your investments earn a single dollar. No other investment offers a guaranteed 50-100% return.

Always contribute at least enough to capture the full employer match. Not doing so is literally leaving free money on the table. If your employer matches 50% of the first 6%, contribute at least 6%. This is the highest-priority investment decision for any employee with a matching 401(k).

Traditional vs. Roth 401(k)

Traditional 401(k) contributions are pre-tax: you get a tax break today, and pay taxes on withdrawals in retirement. Roth 401(k) contributions are after-tax: no tax break today, but withdrawals in retirement (including all gains) are completely tax-free. Both have the same contribution limits.

The choice depends on whether you expect your tax rate to be higher now or in retirement. Younger workers — who are typically in lower tax brackets and have decades of compounding ahead — often benefit more from Roth contributions (pay lower taxes now, enjoy tax-free growth for decades). Higher earners near peak income may benefit from traditional contributions (get the tax break at a high rate, withdraw at a lower rate in retirement).

Contribution Limits

The 2025 employee contribution limit is $23,500 (or $31,000 if you're age 50 or older, thanks to catch-up contributions). Employer matching contributions don't count toward this limit. The total combined limit (employee plus employer) is $70,000. These limits are adjusted periodically for inflation.

Choosing Your 401(k) Investments

Most 401(k) plans offer a limited menu of mutual funds — typically including broad market index funds, bond funds, international funds, and target-date funds. For most participants, a target-date fund (which automatically adjusts its stock-bond mix as you approach retirement) or a low-cost S&P 500 index fund is the best choice.

Avoid high-fee actively managed funds within your 401(k) if low-cost index options are available. A 1% annual fee difference compounds to 25-30% less wealth over a 30-year career. Choose the lowest-cost options that provide broad market exposure.

Your 401(k) handles the diversified, passive core of your retirement portfolio. Individual quality stock selection — using platforms like MoatScope — is best done in a separate IRA or taxable account where you have full control over investment choices. Watch out for plan limitations: some employers offer only expensive fund options. If your plan's cheapest option has fees above 0.50%, lobby HR for better choices — those fees compound into tens of thousands lost over a career.