401(k) Plans Explained: The Match, Vesting, and 2026 Contribution Limits

A 401(k) is a workplace retirement plan that lets you save part of your paycheck, often with a matching contribution from your employer, in an account that grows invested over time. It is the main employer pillar of a US retirement plan and, for many people, the single largest source of retirement savings. Money goes in straight from your pay, gets invested, and grows under generous tax rules until you need it.

I had three of these over my career and barely understood any of them at the time. Looking back, the most expensive thing I did was not grasping the employer match early enough. Here is how a 401(k) works, and the parts worth getting right.

How a 401(k) works

A 401(k) takes a slice of your pay before it reaches your bank account and invests it for retirement. You decide what percentage of your salary to contribute, and your employer routes it into the plan automatically, so you never have to remember to save.

The 401(k) has close cousins that work almost identically: the 403(b) for schools and nonprofits, the 457 for government workers, and the Thrift Savings Plan (TSP) for federal employees and the military. They share the same limits and tax treatment, so most of this guide applies to all of them. See how they sit alongside personal accounts in types of retirement accounts.

The employer match: free money

The employer match is money your company adds to your account when you contribute, and capturing it in full is the most important rule of a 401(k). A typical match might be 50 cents or a dollar for every dollar you put in, up to a set percentage of your salary.

That is an immediate return no investment can promise. If your employer matches up to 5% of pay and you contribute less than 5%, you are turning down part of your own compensation. Whatever else you do, contribute at least enough to get the full match: it is the cornerstone of how much to save for retirement. I cannot get back the match years I missed, and I would tell anyone starting out to grab it from day one.

Auto-enrollment and vesting

Many plans now enroll you automatically and may vest the employer match over time. Auto-enrollment means new employees start contributing by default, often at a modest rate that increases each year, unless they opt out. It is a nudge that has helped millions of people save who otherwise might not have.

Vesting is a rule worth understanding before you ever leave a job. Your own contributions are always 100% yours. The employer match, though, may vest gradually: some plans phase it in over several years, others grant it all at once after a set period. Leave before you are fully vested and you forfeit the unvested match. The U.S. Department of Labor oversees these plan rules, and your plan document spells out your schedule.

Contribution limits for 2026

In 2026 you can contribute up to $24,500 of your own pay to a 401(k). If you are 50 or older, you can add a catch-up contribution of $8,000, bringing your total to $32,500. Under SECURE 2.0, savers aged 60 to 63 get a larger catch-up of $11,250 instead of $8,000.

These caps apply to your own contributions; the employer match sits on top and does not count against them. The limits change most years, so check the current figure with the IRS. We cover all the caps together in retirement contribution limits.

Pre-tax or Roth 401(k)

Many plans let you choose between pre-tax (traditional) and Roth contributions, the same tax decision that runs through every retirement account. Pre-tax contributions lower your taxable income now, and you pay ordinary income tax when you withdraw in retirement. Roth contributions give you no break today but come out completely tax-free later.

A simple guide: lean traditional if you expect a lower tax rate in retirement, and Roth if you expect a higher one, though plenty of people split contributions between the two. We work through the trade-off in traditional vs Roth.

How your 401(k) is invested

A 401(k) is a wrapper; the growth comes from the investments you choose inside it. Most plans offer a menu of mutual funds, very often including low-cost index funds and target-date funds that automatically shift from stocks toward bonds as you near retirement.

Because the money is invested, the value will rise and fall, and it can lose money in any given year; over the long run, that growth is what makes a 401(k) work. Keep an eye on fees, because high expense ratios quietly erode returns over decades, as we explain in retirement account fees. For the bigger picture on funds and risk, see how retirement accounts are invested.

This is general information, not personalized advice, and invested money can lose value. The free official resource is Investor.gov, and for help tailored to your situation see choosing a financial advisor. To see how your 401(k) fits with Social Security and IRAs, start at the retirement planning pillar.