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

A 401(k) is the most common retirement savings account in America — and if your employer offers one, it's usually the first place you should put your money. But a lot of people contribute without fully understanding how it works, what the limits are, or how to actually get the most out of it.

Here's everything you need to know.

What Is a 401(k)?

A 401(k) is an employer-sponsored retirement savings account that lets you contribute a portion of your paycheck before taxes are taken out. Your money grows tax-deferred — meaning you don't pay taxes on it until you withdraw in retirement.

The name comes from the section of the U.S. tax code that created it: Section 401(k).

How Does a 401(k) Work?

Here's the basic flow:

1. You elect to contribute a percentage of your paycheck to your 401(k)
2. That money is deducted before income taxes — lowering your taxable income now
3. Your employer may match a portion of your contributions
4. The money is invested in funds you choose from your plan's options
5. Your investments grow tax-deferred over time
6. In retirement (age 59½ or older), you withdraw the money and pay ordinary income tax on it

The key benefit is the upfront tax break. If you contribute $10,000 this year, you don't pay income tax on that $10,000 now — you pay later, when you withdraw it in retirement.

2026 401(k) Contribution Limits

• Under age 50: $23,500 per year
• Age 50–59 or 63–64: $31,000 per year (catch-up contribution)
• Age 60–63: $34,750 per year (enhanced catch-up under SECURE 2.0)

These limits apply to your contributions only. Employer contributions don't count toward your personal limit.

The Employer Match — Free Money You Shouldn't Leave Behind

Many employers match a portion of what you contribute — typically 50% to 100% of your contributions up to a certain percentage of your salary.

For example: if your employer offers a 100% match up to 4% of your salary and you earn $60,000, contributing $2,400 per year gets you another $2,400 from your employer — free.

This is the closest thing to free money in personal finance. Always contribute at least enough to get the full employer match before putting money anywhere else.

Traditional 401(k) vs. Roth 401(k)

Many employers now offer both options:

	Traditional 401(k)	Roth 401(k)
Tax on contributions	Pre-tax (reduces taxable income now)	After-tax (no upfront deduction)
Tax on withdrawals	Taxed as ordinary income	Tax-free
Required minimum distributions	Yes, starting at age 73	No (starting 2024 under SECURE 2.0)
Best if taxes will be	Lower in retirement	Higher in retirement

If you're early in your career or expect your income to grow significantly, the Roth 401(k) is worth considering. If you're in a high tax bracket now and expect lower income in retirement, the traditional 401(k) wins.

What Can You Invest In?

Unlike an IRA, your investment choices inside a 401(k) are limited to what your employer's plan offers. Most plans include:

• Target-date funds — automatically adjust allocation as you approach retirement
• Index funds — low-cost funds that track the market
• Actively managed mutual funds — higher fees, mixed results
• Bond funds — lower risk, lower return
• Company stock — available in some plans (use with caution)

For most people, a low-cost target-date fund or a simple mix of index funds is the right move.

When Can You Withdraw Without Penalty?

You can withdraw from your 401(k) without penalty starting at age 59½. Withdrawals are taxed as ordinary income.

Withdraw before 59½ and you'll generally owe income tax plus a 10% early withdrawal penalty, with some exceptions:

• Leaving your job at age 55 or older (the "Rule of 55")
• Permanent disability
• Substantially equal periodic payments (SEPP / Rule of 72(t))
• Certain hardship withdrawals

Starting at age 73, you're required to take minimum distributions (RMDs) each year whether you need the money or not.

What Happens to Your 401(k) If You Leave Your Job?

You have four options:

1. Leave it with your old employer — fine if the plan has good funds and low fees
2. Roll it over to your new employer's 401(k) — keeps everything consolidated
3. Roll it over to an IRA — gives you more investment options and control
4. Cash it out — almost always a bad idea; you'll owe taxes and a 10% penalty

Rolling over to an IRA is usually the most flexible option. Just make sure it's a direct rollover to avoid withholding taxes.

How Much Could Your 401(k) Be Worth at Retirement?

If you're 30 years old, earn $60,000, and contribute 10% of your salary with a 4% employer match — investing $8,400 per year total — at a 7% average annual return, you'd have roughly $1.2 million by age 65. All from a consistent habit started early.

Want to see what your 401(k) could look like?

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Common 401(k) Mistakes to Avoid

• Not contributing enough to get the full match — you're leaving free money on the table.
• Cashing out when you change jobs — taxes and penalties will cost you a significant chunk.
• Ignoring your investment choices — defaulting to a money market fund means your money isn't growing.
• Not increasing contributions over time — aim to raise your contribution rate every time you get a raise.
• Borrowing from your 401(k) — 401(k) loans come with risks and opportunity cost that most people underestimate.

Is a 401(k) Worth It?

Yes — almost always. The combination of tax-deferred growth, employer matching, and high contribution limits makes the 401(k) one of the most effective retirement tools available.

The right order for most people: contribute enough to get the full employer match first, then fund a Roth IRA, then come back and max out your 401(k) if you can.

Start early, contribute consistently, and let compound growth do the heavy lifting.