A 401(k) is the most common retirement savings account in the United States. Millions of workers use one, but many do not fully understand how it works, how much they can contribute, or how to get the most from it.
This guide covers everything you need to know about 401(k) plans in 2026, from the basics to contribution limits to investment choices.
What Is a 401(k)?
A 401(k) is an employer-sponsored retirement savings account. The name comes from Section 401(k) of the Internal Revenue Code, which governs how these accounts work.
The core benefit: money you contribute to a traditional 401(k) is taken from your paycheck before taxes are withheld. This reduces your taxable income today and lets your investments grow tax-deferred until you withdraw the money in retirement.
Example: If you earn $60,000/year and contribute $6,000 to a 401(k), you only pay income taxes on $54,000 of income that year. That contribution saves you real money upfront and grows untouched by taxes for decades.
Traditional 401(k) vs Roth 401(k)
Most employers now offer both a traditional and a Roth option within the 401(k) plan.
Traditional 401(k)
- Contributions are pre-tax (reduce taxable income today)
- Investments grow tax-deferred
- Withdrawals in retirement are taxed as ordinary income
- Best for: people who expect to be in a lower tax bracket in retirement than they are today
Roth 401(k)
- Contributions are after-tax (no upfront tax break)
- Investments grow tax-free
- Qualified withdrawals in retirement are completely tax-free
- Best for: people who expect to be in the same or higher tax bracket in retirement, or who are early in their careers
If you are early in your career and currently in a low tax bracket, the Roth 401(k) is almost always the better choice. If you are in your peak earning years and want to reduce taxes now, the traditional option often makes more sense.
401(k) Contribution Limits for 2026
The IRS sets annual contribution limits that adjust periodically for inflation.
- Employee contribution limit (2026): $23,500
- Catch-up contribution (age 50+): Additional $7,500, for a total of $31,000
- SECURE 2.0 enhanced catch-up (ages 60–63): Additional $11,250 instead of $7,500, for a total of $34,750
- Total combined limit (employee + employer contributions): $70,000 (or 100% of compensation, whichever is less)
The 401(k) Employer Match
The employer match is one of the most valuable benefits in the American workplace, and many employees leave it on the table.
A common match structure: the employer matches 50 cents for every dollar you contribute, up to 6% of your salary. If you earn $70,000 and contribute 6% ($4,200), your employer adds $2,100. That is a 50% instant return on $4,200 — no investment beats that.
Always contribute at least enough to get the full employer match. Anything less is leaving free money behind.
How 401(k) Investments Work
When you enroll in a 401(k), your contributions go into investment options selected by your plan. These are usually mutual funds and index funds. Most plans offer:
- Target-date funds (e.g., “Target 2050 Fund”) — automatically adjust asset allocation as retirement approaches
- Stock index funds (e.g., S&P 500 index funds) — broad market exposure at low cost
- Bond funds — lower risk, lower returns
- Stable value or money market funds — very low risk, minimal growth
If you are decades from retirement, allocating heavily toward stock index funds is generally appropriate. The earlier you start, the more time compound growth has to work.
Target-date funds are an excellent default choice if you do not want to manage your own allocation. They automatically shift toward more conservative investments as you approach the target retirement year.
401(k) Fees: What to Watch For
401(k) fees can quietly eat into your retirement balance over time. The two main fee types:
Expense Ratios
This is the annual fee charged by a mutual fund, expressed as a percentage of assets. An index fund might charge 0.03%–0.10%. Actively managed funds often charge 0.5%–1.5% or more. Over 30 years, a 1% higher expense ratio can cost you tens of thousands of dollars.
Whenever possible, choose low-cost index funds over expensive actively managed funds.
Plan Administration Fees
Some employers pass plan administration costs to employees. These show up as a dollar amount deducted from your account periodically. Review your plan’s fee disclosure document (Form 5500 or your plan’s fee schedule) to understand total costs.
401(k) Withdrawal Rules
Age 59½ Rule
You can withdraw from a traditional 401(k) without penalty at age 59½. Withdrawals are taxed as ordinary income.
Required Minimum Distributions (RMDs)
The IRS requires you to start withdrawing from traditional 401(k) accounts at age 73 (as of 2026 under SECURE 2.0 rules). The annual amount is calculated based on your account balance and life expectancy.
Early Withdrawal Penalty
Withdrawing before age 59½ triggers a 10% early withdrawal penalty on top of ordinary income taxes. Exceptions exist for certain hardships, disability, and the “Rule of 55” (leaving a job at age 55 or later and withdrawing from that employer’s plan).
401(k) Loans
Many plans allow you to borrow up to 50% of your vested balance (maximum $50,000) and repay with interest to yourself. This seems attractive but has real drawbacks: the repaid funds lose the tax-advantaged growth opportunity during the loan period, and if you leave your job, the loan often becomes due immediately.
What Happens to a 401(k) When You Change Jobs?
You have four options:
- Roll over to your new employer’s 401(k): Clean and simple. Your money stays in a tax-advantaged account.
- Roll over to an IRA: Usually the best choice. More investment options, potentially lower fees, and full control.
- Leave it in the old employer’s plan: Fine if the plan is good, but you lose the ability to contribute and may face higher fees.
- Cash it out: Almost always a mistake. You pay income taxes plus a 10% penalty, and lose decades of potential compound growth.
When rolling over, request a direct rollover (the check goes straight to the new institution). Do not take the check yourself — the plan withholds 20% for taxes, and you must replace that amount within 60 days to avoid a taxable distribution.
How Much Should You Contribute?
A useful framework:
- Contribute at least enough to get the full employer match. This is step one.
- If you have high-interest debt (credit cards, etc.), pay that off aggressively while keeping step one.
- Once high-interest debt is cleared, max out a Roth IRA ($7,000 in 2026 if under 50).
- After the Roth IRA, increase 401(k) contributions toward the annual maximum ($23,500).
The general target is to save 15% of gross income for retirement, including any employer match. Adjust up if you started late.
Final Thoughts
A 401(k) is one of the most powerful wealth-building tools available to working Americans. The combination of tax advantages, employer matches, and decades of compound growth can turn consistent contributions into a substantial retirement nest egg.
Start by understanding your plan’s investment options and fees, contribute enough to capture the full employer match, and increase contributions over time as your income grows. The earlier you start, the more the math works in your favor.