What Is a 401k? The Complete Guide to Retirement Savings
The 401k is the most powerful retirement savings tool available to American workers — yet millions of employees either don't participate or don't maximize it. Understanding how it works could be worth hundreds of thousands of dollars over your career.
What Is a 401k?
A 401k is an employer-sponsored retirement savings plan that allows employees to contribute a portion of their paycheck before taxes are taken out. Named after Section 401(k) of the Internal Revenue Code, it was established in 1978 and has become the dominant retirement vehicle in America, covering over 60 million active participants.
How Does a 401k Work?
You choose what percentage of your paycheck to contribute, and your employer deducts it automatically before depositing your paycheck. The money goes into investment accounts — typically a selection of mutual funds and ETFs chosen by your employer's plan. Your money grows tax-deferred until withdrawal in retirement.
2024 Contribution Limits
| Category | 2024 Limit |
|---|---|
| Employee contribution (under 50) | $23,000 |
| Catch-up contribution (age 50+) | Additional $7,500 |
| Total limit (employee + employer) | $69,000 |
What Is Employer Matching?
Many employers match a percentage of your contributions — free money added to your retirement account. A common match is 50% of contributions up to 6% of salary. If you earn $60,000 and contribute 6% ($3,600), your employer adds $1,800 — an instant 50% return on that portion.
Traditional 401k vs Roth 401k
| Feature | Traditional 401k | Roth 401k |
|---|---|---|
| Contributions | Pre-tax (reduces income now) | After-tax (no immediate deduction) |
| Growth | Tax-deferred | Tax-free |
| Withdrawals | Taxed as ordinary income | Tax-free in retirement |
| Best for | Higher earners now | Lower earners expecting higher future taxes |
What Is Vesting?
Vesting refers to when employer contributions become fully yours. Your own contributions are always 100% vested immediately. But employer matching may vest gradually — for example, 25% per year over 4 years, or cliff vesting where you get 0% until year 3, then 100% suddenly.
If you leave a job before being fully vested, you forfeit unvested employer contributions. Always check your vesting schedule before resigning.
When Can You Withdraw?
You can withdraw from a 401k penalty-free at age 59½. Early withdrawals incur a 10% penalty plus income taxes. Required Minimum Distributions (RMDs) begin at age 73.
What Happens When You Change Jobs?
You have four options: leave it in your old employer's plan, roll it into your new employer's 401k, roll it into an IRA, or cash it out (least recommended — triggers taxes and penalties). Rolling into an IRA typically gives you the most investment options and lowest fees.
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