A 401(k) is the most widely used retirement savings account in the United States. If your employer offers one, it is usually the single best place to start saving for retirement — the tax advantages and potential employer match are difficult to beat anywhere else. Here is everything you need to know about how 401(k) plans work in 2026.
What Is a 401(k)?
A 401(k) is a tax-advantaged retirement savings account sponsored by your employer. The name comes from the section of the Internal Revenue Code that created it. You contribute money from your paycheck before or after taxes (depending on the type), your investments grow over time, and you withdraw the money in retirement.
In 2026, you can contribute up to $23,500 per year to a 401(k). If you are age 50 or older, you get an additional catch-up contribution of $7,500, bringing your total to $31,000.
Traditional 401(k) vs. Roth 401(k)
Most employers offer both options:
- Traditional 401(k): Contributions are pre-tax. You reduce your taxable income today. You pay taxes when you withdraw in retirement. Better if you expect to be in a lower tax bracket in retirement.
- Roth 401(k): Contributions are after-tax. No immediate tax break, but qualified withdrawals in retirement are completely tax-free. Better if you expect to be in a higher tax bracket in retirement.
If you are unsure which to choose, many financial planners suggest splitting contributions between both to hedge against future tax-rate uncertainty.
The Employer Match: Free Money You Should Not Leave Behind
Many employers match a percentage of what you contribute — for example, 100% of your first 3% of salary or 50% up to 6%. This is the highest guaranteed return available to most workers. If your employer matches and you are not contributing enough to capture the full match, you are leaving compensation on the table.
Example: You earn $60,000. Your employer matches 100% of your first 3% ($1,800/year). If you contribute at least $1,800, you get another $1,800 free. That is an immediate 100% return on those dollars before a single investment grows.
How 401(k) Investments Work
Your contributions go into investment options offered by your plan — typically a selection of mutual funds and target-date funds. You choose how to allocate your money among the available options. Your investments grow tax-deferred (or tax-free in a Roth) until you withdraw.
Most plans include target-date funds (also called lifecycle funds) that automatically adjust their asset allocation as you approach retirement. If you are not confident in selecting your own investments, a target-date fund matching your expected retirement year is a reasonable default.
When Can You Withdraw Without Penalty?
You can take penalty-free withdrawals from a traditional 401(k) starting at age 59½. Withdrawals before that age are subject to a 10% early withdrawal penalty plus ordinary income tax — a combination that can cost you 30–40% or more of the withdrawal amount.
Required Minimum Distributions (RMDs) kick in at age 73 under current law. You must begin withdrawing a minimum amount each year, even if you do not need the money.
What Happens to Your 401(k) When You Leave a Job?
You have four options when you leave an employer:
- Leave it in your old employer’s plan — acceptable if the plan has good investment options and low fees.
- Roll it into your new employer’s 401(k) — consolidates accounts, may give you access to better funds.
- Roll it into an IRA — most common choice. Gives you the widest investment selection and usually lower fees.
- Cash it out — almost always a bad idea. You will owe income taxes plus the 10% penalty if you are under 59½.
When rolling over, request a direct rollover to avoid the 20% mandatory withholding that applies to indirect rollovers.
Solo 401(k) for the Self-Employed
If you are self-employed with no employees (other than a spouse), you can open a Solo 401(k) — also called an Individual 401(k). Contribution limits are significantly higher because you contribute as both employee and employer. In 2026, total contributions can reach up to $70,000 depending on your income.
Bottom Line
If your employer offers a 401(k) with a match, contribute at least enough to capture that match before putting money elsewhere. Then decide between traditional and Roth based on your tax situation. Automate your contributions so you never miss them. The 401(k) is the foundation of most American retirement plans — the earlier you start, the more compounding time your money has.
Related: What Is a 403(b) Plan? 2026 Guide