What Is a 401(k)? How It Works and 2026 Contribution Limits

Employer-sponsored, payroll-deducted, and often matched with free money — here's exactly how a 401(k) works.

A 401(k) is an employer-sponsored retirement account that lets you contribute a portion of your paycheck before it hits your bank account, invest it, and let it grow with tax advantages until retirement. It's named after the section of the tax code that created it, and for most working Americans it's the single largest retirement savings vehicle available, both because of the high contribution limit and because many employers add free money on top in the form of a match.

1. How the payroll deduction actually works

You choose a percentage (or flat dollar amount) of each paycheck to contribute, and your employer deducts it automatically before you ever see the money. With a traditional 401(k), that contribution comes out pre-tax, which lowers your taxable income for the year — contribute $10,000 and your taxable income drops by $10,000. The money is then invested in whatever mix of mutual funds, index funds, or target-date funds your plan offers, and it grows tax-deferred until you withdraw it in retirement, at which point withdrawals are taxed as ordinary income.

2. 2026 contribution limits

The $24,500 employee limit applies across all your 401(k), 403(b), and most 457 plans combined, even if you hold more than one during the year, such as after a job change. The higher combined limit includes everything: your contributions, your employer's match, and any profit-sharing or after-tax contributions your plan allows. Compensation used to calculate contributions is capped at $360,000 for 2026.

One notable 2026 change: if your FICA wages exceeded $150,000 in the prior year, any catch-up contributions you make must go into the Roth side of the plan rather than pre-tax, even if the rest of your contributions are traditional.

3. The employer match: free money with strings attached

Many employers match a portion of what you contribute — a common formula is 50 cents to a dollar for every dollar you contribute, up to some percentage of your salary (often 3–6%). This match doesn't count against your $24,500 employee limit, though it does count toward the $72,000 combined limit. Failing to contribute enough to capture the full match is effectively turning down part of your compensation, which is why financial advisors near-universally recommend contributing at least enough to get it before prioritizing anything else, including debt payoff on anything other than high-interest debt.

4. Vesting: when the match actually becomes yours

Your own contributions are always 100% yours the moment they hit your account. Your employer's contributions are a different story — most plans attach a vesting schedule, meaning you only keep the match if you stay employed long enough. There are two common structures:

• Cliff vesting: you own 0% of employer contributions until a specific milestone (commonly three years), at which point you're 100% vested all at once.
• Graded vesting: you own an increasing percentage each year — for example 20% per year over five years — until you reach 100%.

If you leave before you're fully vested, you forfeit the unvested portion of the employer match back to the plan. This is worth checking before you resign or take a new job, especially if a vesting milestone is only a few months away.

5. Traditional vs. Roth 401(k)

Many plans now offer a Roth 401(k) option alongside the traditional one. The contribution limit is shared between them — you can split your $24,500 however you like, but the combined total can't exceed the limit. A Roth 401(k) contribution is made after-tax, with no upfront deduction, but qualified withdrawals in retirement are entirely tax-free, similar to a Roth IRA but without the income limit. See our complete guide to how a Roth IRA works for the full rules on the IRA version of this same trade-off, including the 5-year rule and early withdrawal exceptions.

6. What happens when you change jobs

Your 401(k) doesn't disappear when you leave a job, but you do need to make an active decision about it. You generally have four options:

1. Leave it where it is, if your old employer's plan allows former employees to stay (many require a minimum balance).
2. Roll it into your new employer's 401(k), consolidating everything in one place.
3. Roll it into an IRA, which typically gives you a much wider choice of investments than a workplace plan.
4. Cash it out, which is almost always the worst option — you'll generally owe ordinary income tax plus a 10% early withdrawal penalty if you're under 59½, on top of losing decades of future tax-advantaged growth.

A direct rollover, where the money moves institution-to-institution without ever passing through your hands, avoids any tax withholding or penalty and is the cleanest way to handle either option 2 or 3.

7. Early withdrawals, hardship withdrawals, and 401(k) loans

Taking money out before age 59½ generally triggers ordinary income tax plus a 10% early withdrawal penalty on top. A few exceptions exist, most notably the "rule of 55" — if you separate from your employer in or after the year you turn 55, you can withdraw from that employer's 401(k) penalty-free, though you'll still owe income tax. Many plans also allow hardship withdrawals for specific qualifying needs, and separately, a 401(k) loan, which lets you borrow from your own balance and repay it with interest back into your own account, avoiding the penalty entirely as long as you repay on schedule — though leaving your job with an outstanding loan balance can trigger it to become due immediately.

8. How much should you actually contribute?

At minimum, contribute enough to capture your full employer match — anything less leaves free money on the table. Beyond that, the right number depends on your broader retirement goal, your other savings vehicles (a Roth IRA is often the next stop after the match, thanks to its wider investment menu), and your timeline. Our guide to figuring out how much you need to retire walks through how to set a real target instead of guessing, and the retirement savings calculator lets you project how your specific contribution rate compounds over time, adjusted for inflation. For the full comparison against IRAs, see 401(k) vs. Roth IRA vs. traditional IRA.

Vesting schedules aren't standardized — check your own plan

There's no universal vesting timeline required by law beyond a maximum allowed schedule; individual employers set their own specific schedule within that limit, and it can range from immediate vesting to a multi-year cliff. Don't assume your plan matches a friend's or a generic example — check your own plan documents or HR for your specific vesting schedule before counting employer contributions as fully yours.

Frequently Asked Questions

How much can I contribute to my 401(k) in 2026?

Employees can contribute up to $24,500 in 2026. Those 50 and older can add a $8,000 catch-up contribution for a total of $32,500. Those 60 to 63 can use a higher $11,250 catch-up instead, for a total of $35,750, if their plan allows it.

What is 401(k) vesting?

Vesting determines how much of your employer's contributions you actually keep if you leave the company. Your own contributions are always 100% yours immediately. Employer contributions typically vest over time, either all at once after a set number of years (cliff vesting) or gradually (graded vesting).

What happens to my 401(k) when I change jobs?

You generally have four options: leave it with your old employer's plan if allowed, roll it into your new employer's 401(k), roll it into an IRA, or cash it out. Cashing out before age 59½ typically triggers income tax plus a 10% early withdrawal penalty, so a rollover is usually the better choice.

Should I choose a traditional or Roth 401(k)?

A traditional 401(k) lowers your taxable income now and taxes withdrawals in retirement. A Roth 401(k) offers no upfront deduction but tax-free withdrawals later. If you expect to be in a similar or higher tax bracket in retirement, Roth tends to make more sense; if you expect a lower bracket, traditional tends to win.

Can I take money out of my 401(k) before retirement?

Early withdrawals before age 59½ generally trigger income tax plus a 10% penalty, though exceptions exist, including the rule of 55 (separating from your employer at 55 or later) and hardship withdrawals. Many plans also allow 401(k) loans, which avoid the penalty if repaid on schedule.

Do I have to contribute enough to get my full employer match?

You're not required to, but it's almost always worth it. An employer match is essentially free money — commonly 50 cents to a dollar for every dollar you contribute, up to a percentage of your pay. Failing to contribute enough to capture the full match means walking away from part of your compensation.