What Is a 401(k) and How Does It Work?

A 401(k) is the main way most Americans save for retirement, and the employer match is close to free money. Here is how contributions, taxes, matching, vesting and withdrawals work.

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For most American workers, the 401(k) is the center of their retirement savings. It has a reputation for being complicated, but the core ideas are simple. Here is what it is and how to use it.

The basics

A 401(k) is an employer-sponsored, tax-advantaged retirement account. You choose to divert a percentage of each paycheck into the account, where it is invested, usually in mutual funds, and grows over decades. The name comes from a section of the tax code.

The tax advantage is the reason it exists, and it comes in two flavors:

• Traditional (pre-tax): contributions come out before income tax, lowering your taxable income now. You pay ordinary income tax later, when you withdraw in retirement.
• Roth: contributions are made with after-tax dollars, so there is no break today, but qualified withdrawals in retirement, including all the investment growth, are tax-free.

Many employers offer both, and you can split contributions between them. Which is better depends largely on whether you expect to be in a higher tax bracket now or in retirement.

The employer match is the headline

Many employers match part of what you contribute, for example 50 cents or a dollar for every dollar you put in, up to a set percentage of your salary. This is as close to free money as personal finance gets.

If your employer offers a match, contributing at least enough to capture the full match is one of the clearest wins in personal finance. Leaving it on the table is a voluntary pay cut.

Vesting: when the match is truly yours

Your own contributions are always 100% yours. The employer match may vest over time, meaning you earn full ownership gradually:

• Cliff vesting: you own 0% of the match until a set date, then 100% all at once (say, after three years).
• Graded vesting: ownership rises in steps, for example 20% per year over several years.

If you leave before you are fully vested, you forfeit the unvested portion of the match, so it pays to know your plan's schedule.

How much you can contribute

The IRS sets annual limits, and they rise most years. For 2026, the employee contribution limit is $24,500. If you are 50 or older, you can add a catch-up contribution of $8,000, for $32,500 total. Under a newer rule, workers who are 60 to 63 get a larger "super catch-up" of $11,250, for $35,750 total. These figures change annually, so confirm the current year's limits.

Getting money out

A 401(k) is meant for retirement, and the rules nudge you to keep it there:

• Withdrawals before age 59.5 generally trigger a 10% early-withdrawal penalty plus income tax, though there are exceptions (disability, certain medical costs, leaving your job in or after the year you turn 55, and others).
• Required minimum distributions now begin at age 73 for traditional balances. Roth 401(k)s no longer have lifetime required distributions.
• When you change jobs, you can roll over your balance into an IRA or your new employer's plan without triggering taxes, as long as it is a direct rollover.

The takeaway

The 401(k) rewards two simple habits: contribute at least enough to get the full match, and start early so compounding has time to work. Everything else, Roth versus traditional, fund choices, catch-up contributions, is a refinement on top of those two moves.

This is general information, not financial advice. Your plan documents and a qualified advisor can address your specific situation.