401(k) Guide — How It Works, Contribution Limits, and Employer Match
How a 401(k) Works
When you enroll in a 401(k), you choose a percentage of your paycheck to contribute. That money goes directly into your account before you ever see it — making it an effortless savings mechanism. You then select investments from a menu of options, typically mutual funds, index funds, and sometimes company stock.
The key advantage is the tax benefit. With a Traditional 401(k), contributions reduce your taxable income today, and you pay taxes when you withdraw in retirement. With a Roth 401(k), you contribute after-tax dollars but withdrawals in retirement are completely tax-free. The right choice depends on whether you expect to be in a higher or lower tax bracket in retirement.
2025 Contribution Limits
| Category | 2025 Limit | Notes |
|---|---|---|
| Employee Contribution (under 50) | $23,500 | Applies to your own salary deferrals |
| Catch-Up Contribution (50-59, 64+) | $7,500 | Additional amount for older workers |
| Super Catch-Up (ages 60-63) | $11,250 | New enhanced catch-up for ages 60-63 |
| Total Limit (Employee + Employer) | $70,000 | Combined maximum including employer match |
| Total Limit (50+ with catch-up) | $77,500 | Including standard catch-up contributions |
Understanding Employer Match
The employer match is free money — and not taking full advantage of it is the single biggest mistake employees make with their 401(k). Common match formulas include 50% of your first 6% (your employer contributes 3% if you contribute 6%) or dollar-for-dollar on the first 3-4%.
Always contribute at least enough to get the full employer match. If your employer matches 50% of the first 6% and you earn $100,000, contributing 6% ($6,000) earns you an additional $3,000 from your employer. That’s an instant 50% return on your money before any market gains.
| Match Formula | Your Contribution | Employer Match | Total Contribution |
|---|---|---|---|
| 50% of first 6% | 6% of salary | 3% of salary | 9% of salary |
| 100% of first 3% | 3% of salary | 3% of salary | 6% of salary |
| 100% of first 4% | 4% of salary | 4% of salary | 8% of salary |
| Dollar-for-dollar up to $5,000 | $5,000 | $5,000 | $10,000 |
Traditional vs. Roth 401(k)
| Feature | Traditional 401(k) | Roth 401(k) |
|---|---|---|
| Tax on Contributions | Pre-tax (reduces current taxable income) | After-tax (no current tax break) |
| Tax on Growth | Tax-deferred | Tax-free |
| Tax on Withdrawals | Taxed as ordinary income | Tax-free (if qualified) |
| Best If… | You’re in a higher tax bracket now than in retirement | You expect higher taxes in retirement |
| RMDs Required? | Yes, starting at age 73 | No (after rollover to Roth IRA) |
| Income Limits | No income limits | No income limits (unlike Roth IRA) |
Choosing Your 401(k) Investments
Most 401(k) plans offer 15-30 investment options. The best approach for most people is to build a simple, diversified portfolio using low-cost index funds. Look for an S&P 500 index fund, an international stock index fund, and a bond index fund. The expense ratio matters enormously — every 0.5% in extra fees can cost you hundreds of thousands of dollars over a career.
Target-date funds are another solid option if you want a hands-off approach. These automatically adjust your asset allocation as you get closer to retirement, shifting from aggressive (more stocks) to conservative (more bonds).
401(k) Withdrawal Rules
| Scenario | Tax Impact | Penalty |
|---|---|---|
| Withdrawal before age 59½ | Income tax on full amount (Traditional) | 10% early withdrawal penalty |
| Withdrawal after age 59½ | Income tax on full amount (Traditional); tax-free (Roth) | No penalty |
| Hardship withdrawal | Income tax applies | 10% penalty may be waived in specific cases |
| 401(k) loan | No tax if repaid on schedule | No penalty if repaid; taxed + penalized if not |
| Required Minimum Distributions (73+) | Taxed as ordinary income | 25% penalty if you miss the RMD deadline |
401(k) Fees — The Silent Killer
When You Leave Your Job
When you change employers, you have four options for your 401(k): leave it in the old plan, roll it into your new employer’s plan, roll it into an IRA (Traditional or Roth), or cash it out (almost always a terrible idea due to taxes and penalties). Rolling into an IRA typically gives you the widest range of investment options and lowest fees.
Key Takeaways
- A 401(k) offers powerful tax advantages for retirement savings — either pre-tax (Traditional) or tax-free growth (Roth).
- Always contribute at least enough to get your full employer match — it’s an instant return on your money.
- Choose low-cost index funds over actively managed options to minimize the drag of fees over decades.
- Avoid early withdrawals before age 59½ — you’ll pay income tax plus a 10% penalty on Traditional balances.
- When changing jobs, roll your old 401(k) into an IRA for better investment options and lower fees.
Frequently Asked Questions
How much should I contribute to my 401(k)?
At minimum, contribute enough to get your full employer match. Ideally, aim to save 15-20% of your income for retirement across all accounts (401k, IRA, etc.). If you can max out the annual contribution limit ($23,500 in 2025), that puts you on a strong path. See our how much to save for retirement guide for detailed calculations.
Should I choose Traditional or Roth 401(k)?
Choose Traditional if you’re in a high tax bracket now and expect to be in a lower bracket in retirement. Choose Roth if you’re early in your career, in a lower bracket now, or expect tax rates to rise. Many financial planners recommend splitting between both for tax diversification. See our Roth vs. Traditional comparison for more details.
What happens to my 401(k) if I get fired or laid off?
Your 401(k) balance is yours. You can leave it in the plan, roll it to a new employer’s plan, roll it into an IRA, or cash it out (not recommended due to taxes and penalties). You typically have 60 days to complete a rollover to avoid taxes and penalties.
Can I withdraw from my 401(k) before retirement?
Yes, but it’s usually costly. Withdrawals before age 59½ are subject to income tax plus a 10% early withdrawal penalty. Some plans allow hardship withdrawals or loans that may reduce or eliminate the penalty in specific situations. Generally, you should leave the money invested.
What is the difference between a 401(k) and an IRA?
A 401(k) is employer-sponsored with higher contribution limits ($23,500 in 2025) and potential employer matching, but limited investment options. An IRA is individually opened with lower limits ($7,000 in 2025) but much wider investment choices. See our 401(k) vs. IRA comparison for a detailed breakdown.