What is a 401(k)?
What you'll learn
Understand what a 401(k) is - the employer-run retirement account funded straight from your paycheck, often with employer money added.
A 401(k) is a retirement account run through your employer. You choose a percentage of your paycheck to defer, and it goes into the account automatically before income tax is taken - so a traditional 401(k) contribution shrinks your tax bill today.
Three things make it work:
- Payroll deferrals - the money moves before it ever reaches your bank account, so saving happens by default.
- The employer match - many employers add their own money when you contribute. That is part of your pay, and you only get it by paying in.
- Tax-deferred growth - investments inside the account grow with no tax along the way. You pay income tax when you withdraw in retirement.
| Feature | How it works |
|---|---|
| Who runs it | Your employer picks the plan and the fund menu |
| How money goes in | Deferred from your paycheck, pre-tax (traditional) |
| Employer match | Many plans add money when you contribute |
| Tax on growth | None while it stays in the account |
| Tax on withdrawal | Income tax in retirement; penalties usually apply before 59 and a half |
The catch: it is locked
The tax perks are the reward for leaving the money alone. Withdraw early and you generally owe income tax plus a 10% penalty. Treat a 401(k) as retirement money, full stop.
There is an annual cap on what you can defer - $24,500 for 2026 under IRS rules. The limit changes most years, so check the current figure in our 401(k) contribution limits guide.
Key takeaways
- A 401(k) is an employer-run retirement account funded straight from your paycheck, pre-tax.
- Many employers match part of what you put in - that match is part of your pay.
- Money grows untaxed until withdrawal; early withdrawals usually cost tax plus a penalty.
- Contribution limits are set by the IRS and change most years, so always check the current figure.
Illustrative only, not a forecast. Assumes $100 growing untouched for 30 years at 7% a year with no tax along the way. Real returns vary and can be negative; tax is due when you withdraw.
Frequently asked questions
Do I pay tax on my 401(k) contributions?
Not upfront in a traditional 401(k). Contributions come out of your paycheck before income tax, and the money grows untaxed. You pay income tax when you withdraw it in retirement. A Roth 401(k) flips this - taxed now, tax-free later.
How much can I put into a 401(k)?
The IRS sets an annual employee limit - $24,500 for 2026, with extra catch-up room from age 50. The limit changes most years, so check the current figure before planning around it.
Can I take the money out whenever I want?
Not without cost. Withdrawals before age 59 and a half generally trigger income tax plus a 10% penalty, with limited exceptions. A 401(k) is designed to stay locked until retirement.
What happens to my 401(k) if I change jobs?
The money is still yours. You can usually leave it in the old plan, roll it into your new employer's plan, or roll it into an IRA. Your own contributions are always fully yours; employer money may depend on vesting.
General information, not financial advice. The value of investments can fall as well as rise, and figures and rules can change; check the current position before acting.