What Is a 401(k)?

November 24, 2025

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What we’ll cover:

A 401(k) is a type of workplace retirement plan that many employers offer as part of their benefits package.
There are two common types of plans: a traditional 401(k) and Roth 401(k); each comes with its own potential tax benefits.
401(k)s come with certain contribution, withdrawal, and RMD rules.

Note: All tax information contained in this article is as of the publication date. Be aware that tax rules are always subject to change, and the IRS website is your official source for the latest forms and guidance.

A 401(k) plan is a type of workplace retirement account that many employers include in their benefits package. If you’re considering a job offer, a 401(k) is an important benefit to look out for because it could help you build a solid nest egg.

At the most basic level, here’s how it works: Once you’ve signed up for a 401(k), you can tell your employer to take a portion of your paychecks (usually a set percentage) and put that money into your 401(k) account where it’ll be invested.

401(k)s are considered tax-advantaged investment accounts. In other words, putting money away in a 401(k) offers potential tax benefits. Ahead, we’ll take a closer look at how a 401(k) works. We’ll start with the basics and then go over a few key contribution and withdrawal rules to keep in mind.

Did you know? These workplace retirement plans are named after a specific part of the Internal Revenue Code: Section 401(k).

How does a 401(k) work? Traditional vs. Roth 401(k)

There are different types of 401(k) plans that employers may offer. (Sometimes, you may see your employer or company being referred to as the “plan sponsor.”) To help keep things simple, we’ll focus on two basic ones that you’re likely to come across at work: a traditional 401(k) and Roth 401(k).

Traditional and Roth plans share many features. Both allow you to contribute a portion of your paychecks and invest that money, letting it potentially grow over time in your 401(k) account. A key difference is how these accounts are taxed.

With a traditional 401(k), you contribute pre-tax dollars through automatic payroll deductions. This is when your employer deducts your 401(k) contribution from your paycheck before taxes are calculated and taken out, which can help lower your taxable income.

Those pre-tax dollars are then put into your 401(k) account where the money can grow tax-deferred. This basically means you don’t have to pay taxes on your contributions and potential earnings until you take the money out (note: you may be subject to an early withdrawal penalty if you take money out before the age of 59½). In short, you could save on taxes up front when you contribute to a traditional 401(k).

A Roth 401(k) essentially operates the opposite way. You contribute to your 401(k) account with after-tax dollars. But generally, withdrawals from your Roth 401(k) are tax-free starting at the age of 59½ (so long as you’ve had the account for five years). Prior to the age of 59½, withdrawals of earnings are generally subject to income tax and a 10% penalty (exceptions may apply).

Traditional vs. Roth 401(k): Is one better than the other?

From a tax perspective, it’s a question of whether you want to pay taxes now (Roth) or later (Traditional). And that may depend, in part, on what you think your retirement future is going to look like. For instance, do you expect to be in a lower or higher tax bracket down the road?

There are many other factors to consider, so it’s a good idea to consult a tax professional or financial advisor if you have any questions about your financial situation.

401(k) investment options. When you sign up for a 401(k) plan, you can usually choose an investment option for your money. The number of options will depend on your plan sponsor. Your employer may enroll you in a default option like a lifecycle or “target-date” fund, which automatically adjusts your mix of investments as you get closer to your target date (for instance, your retirement year).

You can stick with the default option or choose to invest in other types of funds from the plan provider based on your risk tolerance and investment timeline.

401(k) employer match

We mentioned earlier that employers often include a 401(k) plan in their benefits package. When evaluating 401(k) benefits, one question you’ll want to ask is whether there’s an employer match. (Not all companies offer one.)

Some employers may offer to match your 401(k) contributions up to a certain amount each year. The matching formula will vary from company to company. Some places will match dollar for dollar or 50 cents to the dollar up to a certain annual limit.

It’s important to get the details ahead of time so that you can try to get the full match each year. (You work hard—don’t leave any money on the table!)

You’ll also want to ask if there’s a “vesting” period. Many employers require you to stay with the company a few years before the employer contributions become fully vested—that is, yours to take with you when you leave the company.

Key 401(k) rules to keep in mind

Some 401(k) plan details, such as eligibility requirements, investment options, and vesting timeline, will vary from company to company.

When it comes to the rules for things like contribution limits, withdrawals, and required minimum distributions (RMDs), the IRS is your official source for the most up-to-date information. But here are the general rules.

401(k) contribution limits

Like many other types of retirement plans, 401(k)s come with annual contribution limits, meaning you can only contribute a certain amount of money each year.

For 2026, the standard annual contribution limit is $24,500 ($23,500 for 2025). If you’re age 50 or older (and your plan allows it), you could also make so-called “catch-up contributions” to help supercharge your retirement savings.

For example, for 2026, if you’re 50 or older, you could make an additional catch-up contribution of up to $8,000. In other words, you could contribute up to a total of $32,500 ($24,500 + $8,000) to your 401(k) plan in 2026. Visit the IRS website for more information about catch-up contributions.

Important: Under a change made in SECURE Act 2.0, 401(k) plan participants age 60 to 63 will have a higher catch-up contribution limit. The higher catch-up contribution limit for 2026 is $11,250 (instead of $8,000).

Good to know: 401(k) maximum annual contribution limits and rules are subject to change. It’s always a good idea to visit the IRS or consult a tax professional for the most up-to-date information.

401(k) withdrawal rules

Generally speaking, you can start to withdraw from your 401(k) plan (traditional or Roth) penalty-free when you’re 59½ or older. (With a Roth, the account must also have been opened for at least five years.)

This is important: In many cases, if you take money out before the age of 59½, the early withdrawal (or “distribution”) could trigger a 10% penalty. And you may have to pay federal (and state, if applicable) taxes on top of it. But there are exceptions to this early distribution rule. You can visit IRS.gov or consult a tax professional for more information.

See: IRS 401(k) Resource Guide – General Distribution Rules

401(k) RMD rules

“Required minimum distribution” (RMD) is the minimum amount of money you have to withdraw (or “distribute”) from certain types of retirement accounts each year after you’ve reached a specific age.

401(k) plans are subject to RMD rules. In other words, you cannot keep your retirement money in a 401(k) account forever.

However, note that starting in 2024, RMD rules do not apply to Roth 401(k) plan participants while they are alive (but their beneficiaries may have to take RMDs after the account owner’s passing).

Keep in mind that RMDs are required by the IRS, and failure to take RMDs may result in penalties. Visit the IRS website for more information. If you have questions about your specific situation, consult with your financial advisor or a tax professional.

The wrap up

401(k)s can be a great tool to help you save for retirement. If your employer does offer a workplace plan, consider signing up and maximizing your contributions if you can. This could really give your retirement savings a boost, especially if there’s employer matching.

This article is for informational purposes only and is not a substitute for individualized professional tax advice. Individuals should consult their own tax advisor for matters specific to their own taxes. This article was prepared by and approved by Marcus by Goldman Sachs, but does not reflect the institutional opinions of The Goldman Sachs Group, Inc., Goldman Sachs Bank USA, Goldman Sachs & Co. LLC or any of their affiliates, subsidiaries or divisions. Goldman Sachs Bank USA and Goldman Sachs & Co. LLC are not providing any financial, economic, legal, accounting, tax or other recommendations in this article. Information and opinions expressed in this article are as of the date of this material only and subject to change without notice. Information contained in this article does not constitute the provision of investment advice by Goldman Sachs Bank USA, Goldman Sachs & Co. LLC or any of their affiliates. Neither Goldman Sachs Bank USA, Goldman Sachs & Co. LLC nor any of their affiliates makes any representations or warranties, express or implied, as to the accuracy or completeness of the statements of any information contained in this document and any liability therefore is expressly disclaimed. You are not permitted to publish, transmit, or otherwise reproduce this information, in whole or in part, in any format without the express written consent of Goldman Sachs. This foregoing restriction includes, without limitation, using, extracting, downloading or retrieving this information, in whole or in part, to train or finetune a machine learning or artificial intelligence system.