401(k)

Quick Definition

A 401(k) is an employer-sponsored retirement savings plan that allows employees to contribute a portion of their pre-tax salary into investment accounts, reducing their taxable income today while building tax-deferred wealth for retirement. The name comes from the section of the Internal Revenue Code that governs it.

What It Means

The 401(k) is the backbone of private-sector retirement savings in the United States. Before 401(k) plans became widespread in the 1980s, most workers relied on pension plans where employers guaranteed a fixed monthly payment in retirement. Today, the 401(k) shifts the responsibility for retirement savings largely onto the employee.

Contributions go in before federal and state income taxes are calculated. If you earn $70,000 and contribute $7,000 to a 401(k), you only pay income tax on $63,000 that year. The investments grow tax-deferred, meaning you pay no tax on dividends, interest, or capital gains inside the account while they compound. You only pay income tax when you withdraw money in retirement, at which point your tax rate is often lower.

How It Works

Step-by-Step Process

1. Enroll through your employer's HR department or benefits portal
2. Choose your contribution percentage of each paycheck (e.g., 6% of salary)
3. Select your investments from the menu your employer's plan offers (typically mutual funds, index funds, and target-date funds)
4. Contributions deducted automatically from each paycheck before taxes
5. Investments grow tax-deferred over time through compounding
6. Employer may match a portion of your contributions (free money)
7. Withdraw in retirement (age 59½+) and pay ordinary income tax on withdrawals

2025 Contribution Limits

The Employer Match: The Most Important Number

The employer match is the most powerful feature of a 401(k) and represents an immediate, guaranteed 50-100% return on your investment. No asset class on earth reliably delivers that.

How Matching Works

Common match formula: 100% of contributions up to 3% of salary, plus 50% of contributions from 3-5% of salary.

Example calculation:

The critical rule: Always contribute at least enough to get the full employer match. Not doing so is leaving a portion of your compensation on the table.

Vesting Schedules

Employer match contributions may not be immediately yours. Most employers use a vesting schedule:

Your own contributions are always 100% vested immediately. The vesting schedule only applies to employer contributions. Leaving a job before you are fully vested means forfeiting unvested employer contributions.

The Power of Tax-Deferred Growth

Calculation Example

Scenario: You contribute $500/month to a 401(k) vs. a taxable account, both earning 7% annually, over 30 years. Assume a 24% marginal tax rate.

The 401(k) wins by roughly $86,000 in this example, purely from the tax-deferred compounding advantage and the upfront tax savings.

Investment Options

Most 401(k) plans offer a limited menu of investment options selected by your employer. Common options include:

Target-date funds are the simplest option: pick the fund closest to your expected retirement year (e.g., "Target 2055 Fund") and it automatically becomes more conservative as you approach retirement.

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

Many employers now offer both options:

Practical rule of thumb: If you are early in your career and in a low tax bracket, lean toward the Roth 401(k). If you are a high earner in your peak earning years, the traditional pre-tax 401(k) gives you a bigger tax break now.

Withdrawals, Penalties, and Required Minimum Distributions

Early Withdrawal (Before 59½)

Withdrawing before age 59½ triggers a 10% early withdrawal penalty on top of ordinary income tax. On a $20,000 withdrawal at a 22% tax rate, that means:

• Income tax: $4,400
• Penalty: $2,000
• Total cost: $6,400 (32% of the withdrawal)

Exceptions to the penalty include disability, certain medical expenses, substantially equal periodic payments (SEPP/72(t)), and certain first-time home purchases (in Roth 401k only).

Required Minimum Distributions (RMDs)

Starting at age 73, the IRS requires you to begin taking minimum withdrawals from a traditional 401(k) whether you want to or not. The RMD amount is calculated by dividing your account balance by a life expectancy factor from IRS tables.

Failing to take your RMD results in a 25% excise tax on the amount you should have withdrawn (reduced to 10% if corrected promptly).

Real-World Example: The Cost of Not Contributing

Two colleagues, both earning $65,000, both age 25:

• Alex contributes 6% ($3,900/year) with a 3% employer match ($1,950/year). Total: $5,850/year.
• Jordan contributes nothing, spending the extra $3,900/year.

At age 65, assuming 7% average annual return:

Jordan would need to save an extraordinary amount in taxable accounts to match what Alex built through consistent, employer-matched, tax-deferred contributions.

Key Points to Remember

• Always get the full employer match first before any other investment decision
• Contribution limits reset every January 1 - you cannot contribute extra to make up for prior years
• Investment selection matters enormously over 30-40 years; low-cost index funds typically outperform actively managed funds
• Leaving a job means you can leave the 401(k) with the old employer, roll it to a new employer's plan, or roll it to an IRA
• Loans from 401(k) are allowed by most plans but risky - if you leave the job, the loan may become due immediately

Common Mistakes to Avoid

• Not contributing enough to get the full match: This is the single most common and costly mistake.
• Cashing out when changing jobs: Rolling over to an IRA or new employer's plan avoids taxes and penalties.
• Ignoring investment selection: Leaving money in a default money market fund for decades destroys long-term returns.
• Not increasing contributions after raises: Automate contribution increases each year.
• Borrowing from your 401(k): Loans interrupt compounding and create risk if you leave the job.

Frequently Asked Questions

Q: What happens to my 401(k) if my employer goes bankrupt? A: Your 401(k) assets are legally separate from the company's assets and are held in a trust. If your employer goes bankrupt, creditors cannot touch your 401(k) balance. The plan assets belong to you.

Q: Can I contribute to both a 401(k) and an IRA? A: Yes. You can max out a 401(k) and also contribute to a Roth or traditional IRA in the same year, subject to IRA income limits and contribution caps.

Q: What is a "safe harbor" 401(k)? A: A safe harbor plan is designed to automatically pass certain IRS non-discrimination tests. Employers typically must make mandatory contributions to all eligible employees. These plans are common at smaller businesses.

Q: How do I find out what investments my plan offers? A: Log into your plan's website (administered by Fidelity, Vanguard, Empower, or similar) and look under "investment options" or "fund lineup." You can compare expense ratios and historical performance there.