What a 401(k) is and how money moves into it

A 401(k) is a retirement savings account that your employer sets up for you. Money comes out of your paycheck before taxes are taken out, goes into an investment account held in your name, and stays there until you reach retirement age. The account is named after a section of the tax code that created it.

Here is how the money flow works: you tell your employer what percentage of each paycheck to send to your 401(k) — say, 5 percent. That money never hits your bank account. Instead, it goes straight into your 401(k) account, where it is invested in funds you choose (usually mutual funds or target-date funds). Your employer may also add money to your account as a match — for example, 50 cents for every dollar you contribute, up to 6 percent of your salary.

The money grows over time because the investments earn returns. You do not pay income tax on that growth until you withdraw the money in retirement. This tax delay is the main reason employers offer 401(k)s: it lets you save more because you are not paying taxes on the money right now.

Key Takeaways

  • A 401(k) is a retirement account where money comes out of your paycheck before taxes, gets invested, and grows tax-free until you withdraw it.
  • Your employer chooses the investment options available to you, usually a menu of 10 to 30 mutual funds or target-date funds.
  • Many employers match a portion of what you contribute — commonly 50 cents per dollar up to 6 percent of your salary — which is information programs you should try to capture.
  • You cannot withdraw money before age 59½ without paying a 10 percent penalty, with narrow exceptions for hardship or leaving your job after age 55.
  • When you leave your job, you can roll the 401(k) into an IRA or into your new employer's plan to keep the money growing tax-free.

How much you can contribute and what your employer might add

The IRS sets a limit on how much you can contribute each year. This limit changes annually and is higher if you are 50 or older. You can find the current limit on the IRS website or ask your HR department. Most people contribute between 3 and 10 percent of their salary, but you can contribute more if you want to — up to the IRS limit.

Your employer's match is separate from your contribution limit. If your employer offers a match, it is usually described as a percentage of your salary. A common match is "100 percent of the first 3 percent you contribute, and 50 percent of the next 3 percent" — meaning if you contribute 6 percent of your salary, your employer adds 4.5 percent. That match is information programs, and it is one of the best reasons to contribute to a 401(k) even if you are not sure about retirement saving yet.

Not all employers offer a match. Some offer a flat contribution (like 3 percent of your salary, whether you contribute or not), and some offer nothing. Check your plan documents or ask HR what your employer provides.

The investment choices your plan offers

When you enroll in your 401(k), you choose how your money is invested from a menu your employer provides. Most plans offer 10 to 30 options, usually mutual funds or target-date funds. A target-date fund is a single fund that automatically adjusts its mix of stocks and bonds as you get closer to retirement — you pick the fund with the year closest to when you plan to retire, and it does the rest.

If you do not choose an investment, your plan may automatically put your money into a target-date fund based on your age, or into a stable value fund that does not grow much but does not lose money either. This is called a default investment. It is not ideal, but it is better than leaving money in cash.

You can change your investment choices once a year, or sometimes more often. If you are new to investing, a target-date fund is a straightforward choice. If you want more control, you can build your own mix of stock funds and bond funds, but that requires more knowledge.

When you can take money out and what happens if you do

You can withdraw money from your 401(k) without penalty once you reach age 59½. Before that age, withdrawals are subject to a 10 percent penalty on top of income tax. There are a few exceptions: you can withdraw without penalty if you leave your job after age 55, if you have a serious financial hardship (defined narrowly by the IRS), or if you are disabled. Some plans also allow loans against your balance, though you have to pay the loan back with interest.

Hardship withdrawals are not straightforward to get. The IRS requires that you have an when ready and heavy financial need — like unpaid medical bills, eviction, or funeral costs — and that you have no other way to pay for it. Your employer's plan decides whether to allow hardship withdrawals at all, and the process takes time.

If you leave your job before 59½, do not withdraw the money. Instead, roll it over into an IRA or into your new employer's 401(k). A rollover moves the money without triggering taxes or penalties, and it keeps growing tax-free. If you withdraw the money directly, you will owe income tax plus the 10 percent penalty.

What happens to your 401(k) when you leave your job

When you leave your employer, your 401(k) stays in your name — your employer does not take it back. You have four choices: leave it where it is, roll it into an IRA, roll it into your new employer's 401(k), or withdraw it (which triggers taxes and penalties if you are under 59½).

Most people roll the money into an IRA because IRAs often have lower fees and more investment choices than 401(k)s. Your new employer's plan is a good choice if the fees are low and the investment options are good. Leaving the money in your old employer's plan is fine if you like the investments and the fees are reasonable, but you will have to keep track of an extra account.

A rollover is straightforward: you contact the new IRA provider or new employer's plan, and they handle moving the money directly from your old 401(k). You do not touch the money yourself — if you do, it becomes a taxable withdrawal.

Fees and how they affect your balance over time

Your 401(k) charges fees for managing the account and for each fund you invest in. These fees are usually small — often less than 1 percent of your balance per year — but they add up over decades. A fund that charges 1 percent per year costs you significantly more than a fund that charges 0.2 percent, especially if you are saving for 30 or 40 years.

Your plan statement shows the fees you are paying, usually listed as an expense ratio for each fund. Ask your HR department for a summary of all plan fees, including administrative fees. If your plan's fees seem high, you may want to choose lower-cost funds if they are available, or ask HR whether the plan is shopping for lower-cost providers.

How taxes work when you retire and start withdrawals

When you withdraw money from your 401(k) in retirement, that money is taxed as ordinary income. If you contributed $10,000 per year for 30 years and your balance grew to $500,000, you will owe income tax on the full $500,000 as you withdraw it — not just on the growth.

You do not have to withdraw all the money at once. You can take out as much or as little as you want each year, as long as you start taking required minimum distributions at age 73 (this age changes periodically, so check the current rule). The amount you withdraw each year is added to your other income and taxed at your tax rate for that year.

Some people withdraw less in years when their income is low, and more in years when they have other income. This is called tax planning, and it can save you money. A tax professional can help you figure out the best withdrawal strategy for your situation.

Frequently Asked Questions

What is the difference between a 401(k) and an IRA?

A 401(k) is offered by your employer and often includes an employer match. An IRA is an account you open yourself and has higher contribution limits if you are 50 or older. You can have both at the same time. Most people prioritize getting the full employer match in their 401(k) first, then contribute to an IRA if they want to save more.

Can I borrow money from my 401(k)?

Some plans allow loans against your balance, usually up to 50 percent of what you have saved or $50,000, whichever is less. You have to pay the loan back with interest, usually over five years. If you leave your job before the loan is repaid, you typically have to pay it back quickly or it becomes a taxable withdrawal. Loans should be a last resort because they reduce the money growing for retirement.

What happens to my 401(k) if I die?

Your 401(k) goes to whoever you named as a beneficiary on your account. If you did not name anyone, it goes to your estate and may go through probate. You can change your beneficiary anytime by contacting your HR department. Make sure the name and Social Security number are correct so the money reaches the right person.

Can I contribute to a 401(k) if I am self-employed?

No, a 401(k) is only available through an employer. If you are self-employed, you can open a Solo 401(k) or a SEP IRA, which work similarly but are set up for one-person businesses. Talk to a tax professional or financial advisor about which option makes sense for your situation.

Should I invest in my company's stock through the 401(k)?

Most financial advisors suggest keeping your company stock to no more than 10 percent of your 401(k) balance. If your company struggles, you could lose both your job and a big chunk of your retirement savings at the same time. Diversifying across many companies and industries reduces that risk.