What is a 401(k) in simple terms?

A 401(k) is a workplace retirement savings account in the United States, named after the section of the US tax code that created it. You contribute pre-tax money from your paycheck — reducing your taxable income today — and the money grows tax-deferred until you withdraw it in retirement. Many employers also match a portion of your contributions, which is effectively free money. In 2025, you can contribute up to $23,500 per year ($31,000 if you're 50 or older).

What is the 401k contribution limit for 2025?

For 2025, the employee 401(k) contribution limit is $23,500. If you are aged 50 or older, you can make an additional catch-up contribution of $7,500, for a total of $31,000. The combined employee + employer contribution limit (total additions limit) is $70,000 for 2025. These limits are set by the IRS and typically increase each year to keep pace with inflation.

Should I contribute to a traditional or Roth 401(k)?

The key question: do you expect to be in a higher or lower tax bracket in retirement? Traditional 401(k): you pay no tax now, but pay your future tax rate on withdrawals. Better if you're in a high tax bracket today and expect to be in a lower one in retirement. Roth 401(k): you pay tax now at your current rate, but withdrawals in retirement are completely tax-free. Better if you're early in your career (lower tax bracket now) or expect your tax rate to rise.

401(k) Guide 2025 — What It Is & How to Maximise It

What Is a 401(k)?

A 401(k) is a tax-advantaged retirement savings plan offered by employers in the United States. The name comes from Section 401(k) of the Internal Revenue Code. You contribute a portion of your pre-tax salary directly into the account, reducing your taxable income today. The money then grows tax-deferred — meaning you pay no tax on gains, dividends, or interest while the money remains in the account. Tax is paid only when you make withdrawals in retirement.

The biggest advantage most employees have: employer matching. Many employers match a portion of your 401(k) contributions — typically 50–100% of contributions up to 3–6% of salary. This is effectively free money that immediately doubles your return on those contributions. Always contribute at least enough to capture the full employer match.

If your employer matches 100% of contributions up to 3% of your salary and you earn $60,000, contributing 3% ($1,800) gives you $1,800 in employer contributions — an instant 100% return. No investment strategy can reliably beat that. Always capture the full employer match before allocating extra savings elsewhere.

2025 Contribution Limits

Employee limit (under 50)

$23,500

Per year, employee contributions only

Catch-up (age 50+)

+$7,500

Total $31,000 for those 50 and older

Total additions limit

$70,000

Employee + employer combined maximum

Traditional vs Roth 401(k)

Many employers now offer both a traditional (pre-tax) 401(k) and a Roth 401(k) option. The difference is when you pay tax:

Traditional 401(k)

Pay tax later

Contributions reduce taxable income now

Growth is tax-deferred

Withdrawals in retirement taxed as ordinary income

Required Minimum Distributions from age 73

Good if: high tax bracket now, lower in retirement

Best for: peak earners, higher brackets today

Roth 401(k)

Pay tax now, withdraw tax-free

Contributions made with after-tax dollars

Growth is completely tax-free

Qualified withdrawals in retirement are tax-free

No Required Minimum Distributions (Roth)

Good if: lower bracket now, higher in retirement

Best for: early career, expecting income to grow

Understanding Employer Matching

Employer match formulas vary. The most common examples:

100% match up to 3% of salary: If you earn $70,000 and contribute 3% ($2,100), employer adds $2,100. Total: $4,200 annual contribution.
50% match up to 6% of salary: Contribute 6%, employer adds 3%. To get the full match, you must contribute the full 6%.
Dollar-for-dollar up to $5,000: Some employers cap the match in dollar terms rather than percentage.

⚠️ Vesting schedules

Your own contributions are always 100% yours immediately. Employer contributions may be subject to a vesting schedule — meaning you only keep them after working for the company for a certain period. "Cliff vesting" means you get 0% until you've worked there 3 years, then 100% immediately. "Graded vesting" gradually increases your ownership percentage over time. If you're considering leaving a job, check your vesting schedule first — leaving before you're fully vested means forfeiting unvested employer contributions.

What to Invest In Inside Your 401(k)

Most 401(k) plans offer a menu of mutual funds and target-date funds. Key considerations:

Target-date fund (simplest option): A "2050 fund" or "2055 fund" automatically adjusts from equities to bonds as you approach retirement. Set it, contribute regularly, and forget it. Suitable for most employees.
Low-cost index funds: If your plan offers S&P 500 index funds or total market index funds at 0.05–0.20% expense ratio, these are excellent. Avoid high-fee actively managed funds (above 0.5% expense ratio).
Check the expense ratios: Every fund in your plan should have a disclosed expense ratio. Compare options — two funds tracking similar indexes may have very different costs. Over 30 years, a 1% difference in fees is significant.

✅ The 401(k) priority order

1. Contribute enough to get the full employer match — always first.
2. Max out a Roth IRA ($7,000 limit in 2025) — more investment flexibility, backdoor option.
3. Return to 401(k) and contribute up to the annual limit ($23,500).
4. After-tax investments in a taxable brokerage account.

Withdrawals, Penalties and RMDs

You can withdraw from a traditional 401(k) without penalty starting at age 59½. Early withdrawals (before 59½) incur a 10% penalty on top of ordinary income tax — making early withdrawals very expensive. Exceptions include death, disability, "substantially equal periodic payments," and certain hardship withdrawals.

At age 73, traditional 401(k) holders must begin taking Required Minimum Distributions (RMDs) — mandatory annual withdrawals calculated by the IRS based on your account balance and life expectancy. Failure to take RMDs results in a 25% penalty on the amount you should have withdrawn.

Roth 401(k) accounts no longer require RMDs after the SECURE 2.0 Act changes (effective 2024) — another advantage over traditional accounts for those who want to pass wealth to heirs.

Frequently Asked Questions

Yes — contributing to a 401(k) doesn't prevent you from also contributing to a Roth or Traditional IRA. The IRA limit for 2025 is $7,000 ($8,000 if 50+). However, whether you can deduct Traditional IRA contributions from your taxes depends on your income and whether you (or your spouse) are covered by a workplace plan. Roth IRA contributions phase out at higher incomes ($150,000 for single filers in 2025, though the "backdoor Roth" strategy works around this).

You have four options: (1) Leave it with the old employer (some allow this; others require you to move it once below a threshold); (2) Roll it over into your new employer's 401(k) plan; (3) Roll it over into an IRA — this gives you more investment choice and often lower fees; (4) Cash it out — avoid this: you'll pay income tax plus a 10% early withdrawal penalty. Rolling to an IRA is usually the most flexible option and avoids all taxes and penalties when done as a direct rollover.

Many 401(k) plans allow you to borrow from your own balance — typically up to 50% of your vested balance or $50,000, whichever is less. You repay with interest (to yourself). The problem: while the money is out of the market, it isn't compounding. If you leave your job, the loan typically becomes due immediately — and if you can't repay, it's treated as a distribution with taxes and penalties. Use 401(k) loans only in genuine emergencies.

Important: US tax law and retirement account rules are complex and subject to change. Figures shown are for 2025 and may change. This is educational content only — consult a CPA or fee-only financial adviser for advice specific to your situation.