What happens when you contribute to a 401(k)

When you enroll in your employer's 401(k) plan, money moves directly from your paycheck into an investment account before taxes are taken out. Your employer sends that money to a plan administrator — a financial company like Fidelity, Vanguard, or Charles Schwab — who holds it and invests it according to your choices. You pick from a menu of investment options, usually mutual funds or target-date funds, and your contributions buy shares in those funds. The money stays in that account and grows (or sometimes shrinks) based on how those investments perform.

Your employer may also contribute money to your account through a matching program. A common match is 50 cents for every dollar you contribute, up to 3% or 6% of your salary. That employer money is information programs — it goes into the same account and follows the same investment rules as your contributions. Some employers offer a flat match instead, like $500 per year regardless of how much you contribute.

The account grows tax-free while the money sits there. You do not pay income tax on the growth, the dividends, or the interest until you withdraw the money in retirement. That tax delay is the main reason a 401(k) saves you money compared to a regular savings account.

Key Takeaways

  • Money you contribute to a 401(k) comes out of your paycheck before income tax is calculated, which lowers your taxable income for the year.
  • Your employer chooses the plan administrator and the investment options available to you, so your choices depend on where you work.
  • An employer match is a percentage of your salary that your employer adds to your account if you contribute, and it is the closest thing to information programs in retirement savings.
  • The money grows tax-free inside the account, but you owe income tax on withdrawals after age 59½, and you cannot touch the money before then without a penalty in most cases.
  • You decide how much of each paycheck goes into the plan, and you can change that choice once per year or when your life circumstances change.

How much you can contribute and when

The IRS sets a yearly limit on how much you can put into a 401(k). That limit changes most years, so check your plan documents or ask your HR department for the current year's number. Your employer's plan administrator will also show you the limit when you enroll. You choose a percentage of your salary or a dollar amount per paycheck, and that money comes out automatically until you change it or the year ends.

If your employer offers a match, you want to contribute at least enough to get the full match. If you contribute less than the match threshold, you are leaving information programs on the table. For example, if your employer matches 50 cents on the dollar up to 6% of your salary, and you only contribute 3%, your employer only adds 1.5% — you missed out on 1.5% in matching funds.

You can change your contribution amount once per year during the plan's open enrollment period, which is usually in the fall. You can also change it if you have a life event — marriage, divorce, birth of a child, or a significant change in income. Your HR department can tell you the exact dates and what counts as a may have access to event.

Investment choices and how your money is invested

When you enroll, you choose how to split your contributions among the investment options your plan offers. A typical plan might offer 15 to 30 different funds. Most plans include a target-date fund, which automatically adjusts its mix of stocks and bonds as you get closer to retirement — more aggressive when you are young, more conservative as you near 60. Many people choose a single target-date fund and let it do the work.

Other common options are stock funds (which own shares in companies), bond funds (which own debt issued by companies and governments), and money market funds (which are very stable but grow slowly). Some plans also offer a self-directed brokerage option, which lets you pick individual stocks or other investments, though this is less common and usually costs extra.

Your choice of investments matters because different funds grow at different rates. A fund heavy in stocks might double in value over 20 years but could lose 30% in a bad year. A bond fund grows more slowly but is less likely to lose money. The plan administrator provides a prospectus or fact sheet for each fund showing its past performance, fees, and what it invests in. Read these before you choose, or ask your HR department or a financial advisor for guidance.

Vesting: when the employer match becomes yours

Your own contributions are always yours when ready — you can take them with you if you leave the job. Employer matching money, however, often comes with a vesting schedule. Vesting means the employer's contributions gradually become yours to keep. A common schedule is 20% per year, so after five years of employment, 100% of the match is yours. Some employers use a cliff schedule, where you get nothing until you hit a certain year (often three years), then you get 100% all at once.

If you leave your job before you are fully vested, you forfeit the unvested portion of the employer match. That money stays in the plan and is used to reduce future employer contributions for other employees. This is why it matters to know your vesting schedule — if you are close to being fully vested and considering a job change, staying a few more months might be worth thousands of dollars.

Your plan documents will show your vesting schedule, and your plan administrator can tell you exactly how much of the employer match you have vested at any time. Ask HR or your plan administrator for this information if you are thinking about leaving.

Withdrawals before retirement and the 59½ rule

In most cases, you cannot withdraw money from a 401(k) before age 59½ without paying a 10% penalty on top of the income tax you owe. That penalty is in addition to the regular income tax, so a withdrawal at age 45 could cost you 30% to 40% of the amount you take out, depending on your tax bracket. The money you withdraw is added to your income for that year, which can push you into a higher tax bracket.

There are a few exceptions where you can withdraw without the 10% penalty. These include a "hardship withdrawal" for certain financial emergencies (the rules are strict and vary by plan), a withdrawal after you leave your job if you are 55 or older, or a withdrawal to pay for a may have access to medical expense or health insurance after a job loss. Some plans also allow loans, where you borrow from your own 401(k) balance and pay yourself back with interest — you do not owe taxes on a loan, but if you leave your job before you repay it, the loan balance is treated as a withdrawal and taxed.

The 59½ age rule is federal law, so it applies to every 401(k). Your plan may have stricter rules, so check your plan documents or ask your administrator what withdrawals are allowed before retirement age.

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

When you leave your employer, your 401(k) stays with the plan administrator — it does not disappear. You have several options for what to do with it. You can leave it where it is if your balance is above a certain amount (usually $5,000), though you may not be able to make new contributions or change your investments. You can roll it over into an IRA (Individual Retirement Account) at a bank or brokerage, which gives you more investment choices and often lower fees. You can roll it into your new employer's 401(k) if they offer one. Or you can cash it out, though this triggers taxes and the 10% penalty if you are under 59½.

A rollover is usually the best option because it keeps the money growing tax-free and avoids the when ready tax hit. If you roll over to an IRA, make sure to do a "direct rollover" where the money moves from the old plan administrator to the new one without passing through your hands. If the money lands in your personal account first, even for a day, it is treated as a distribution and you owe taxes on it.

Your old plan administrator will send you paperwork explaining your options and the important date to make a choice. Do not ignore this paperwork — if you do not respond, the plan may cash out your balance and send you a check, which triggers taxes and penalties.

Required withdrawals after age 72

Once you reach age 72, the IRS requires you to withdraw a minimum amount from your 401(k) each year, called a Required Minimum Distribution or RMD. The amount is calculated based on your age and your account balance. If you do not take the RMD, you owe a 25% penalty on the amount you should have withdrawn (this penalty was reduced from 50% in recent years, but it is still steep). The RMD is added to your income for the year and is taxed as ordinary income.

If you are still working at age 72 and do not own more than 5% of the company, you may be able to delay RMDs until you retire. This is called the "still-working exception." Your plan administrator can tell you whether your plan allows this. Once you do retire, RMDs begin the following year.

Frequently Asked Questions

Can I contribute to a 401(k) and an IRA at the same time?

Yes, you can contribute to both in the same year. However, if you have a 401(k) through your employer, your ability to deduct contributions to a traditional IRA on your taxes may be limited depending on your income. A Roth IRA has no such limit. Talk to a tax professional or your plan administrator about how this affects your taxes.

What happens to my 401(k) if I get fired or laid off?

Your 401(k) is yours — it does not disappear or get forfeited because you lost your job. You keep the money you contributed and any employer match that was vested. You will need to decide what to do with the account: leave it, roll it over to an IRA, or roll it into a new employer's plan. Your old plan administrator will contact you with your options.

Can I borrow from my 401(k)?

Many plans allow loans, but not all. If your plan allows it, you can usually borrow up to 50% of your vested balance, up to $50,000. You repay the loan with interest, and the interest goes back into your account. If you leave your job before repaying the loan, the remaining balance is treated as a withdrawal and taxed. Check your plan documents to see if loans are available.

What is the difference between a traditional 401(k) and a Roth 401(k)?

A traditional 401(k) reduces your taxable income now, and you pay taxes when you withdraw in retirement. A Roth 401(k) does not reduce your taxable income now, but withdrawals in retirement are tax-free. Not all employers offer a Roth option. If yours does, the choice depends on whether you think your tax bracket will be higher or lower in retirement.

What fees does a 401(k) charge?

Plans charge administrative fees (paid by the employer or deducted from your account), investment fees (charged by the fund companies), and sometimes advisor fees if you use a financial advisor. Your plan documents list these fees. Compare them when you choose investments — a fund with a 1.5% annual fee costs significantly more over time than one with a 0.15% fee.