A pre-tax 401(k) lets you contribute money to retirement before income tax is taken out, which lowers the income you report to the IRS that year

When you put money into a pre-tax 401(k), your employer deducts it from your paycheck before calculating federal income tax. That means if you earn $50,000 and contribute $6,000 to a pre-tax 401(k), you only report $44,000 as taxable income. You pay income tax on the smaller number, not the full salary.

The money sits in your 401(k) account and grows over time. You do not pay tax on the growth while the money is invested. When you withdraw the money in retirement, that is when you pay income tax on the full amount — both what you put in and what it earned.

This is different from a Roth 401(k), where you contribute after-tax dollars (you pay income tax now) but withdrawals in retirement are tax-free. Most people choose pre-tax when they expect to be in a lower tax bracket after they retire.

Key Takeaways

  • Pre-tax 401(k) contributions reduce your taxable income in the year you contribute, which usually means a smaller tax bill or a larger refund.
  • You pay income tax on the money when you withdraw it in retirement, not when you contribute it.
  • Your employer may match a portion of your pre-tax contributions, and that match is also not taxed until withdrawal.
  • The IRS sets annual limits on how much you can contribute; for 2024 the limit is $23,500 for people under 50.
  • You cannot withdraw pre-tax 401(k) money before age 59½ without penalty unless you meet specific exceptions like hardship or separation from service.

How the tax savings work in practice

Suppose you earn $60,000 a year and your employer offers a 401(k) plan. You decide to contribute $300 per paycheck (about $7,800 per year). Your employer withholds that $300 before calculating income tax on your paycheck.

Instead of paying federal income tax on $60,000, you pay it on $52,200. If your federal tax rate is 12 percent, you save about $936 in federal income tax that year. You also save on Social Security and Medicare taxes (combined 7.65 percent), which adds another $597 in savings. That is $1,533 you keep instead of sending to the government — money that stays in your 401(k) to grow.

Your state may also tax income. If you live in a state with income tax, a pre-tax 401(k) contribution reduces that too. The exact savings depend on your state's tax rate and your income level.

The difference between pre-tax and Roth 401(k)

A pre-tax 401(k) reduces your taxes now. A Roth 401(k) reduces your taxes later. Many employers offer both, and you can split your contributions between them.

With pre-tax, you pay tax when you retire and withdraw the money. With Roth, you pay tax now (on the money before it goes into the account) and pay nothing when you withdraw in retirement. Choose pre-tax if you think your tax rate will be lower in retirement. Choose Roth if you think your tax rate will be higher, or if you want to lock in today's tax rate and avoid surprises later.

One major difference: Roth 401(k)s have required minimum distributions (RMDs) starting at age 73. You must withdraw a certain amount each year and pay tax on it, even if you do not need the money. Pre-tax 401(k)s also have RMDs. Roth IRAs do not, which is one reason some people convert pre-tax 401(k) money to a Roth IRA in retirement.

Employer matching and pre-tax contributions

Many employers match a portion of your 401(k) contribution — often 50 percent of what you contribute, up to 6 percent of your salary. If you earn $50,000 and contribute 6 percent ($3,000), your employer adds $1,500. That match is information programs and is also treated as pre-tax, meaning you do not pay income tax on it until you withdraw.

The match is one reason financial advisors often recommend contributing at least enough to get the full match. If your employer matches 50 percent up to 6 percent of salary and you only contribute 3 percent, you are leaving half the match on the table.

Contribution limits and catch-up contributions

The IRS sets an annual limit on how much you can contribute to a 401(k). For 2024, the limit is $23,500 if you are under age 50. If you are 50 or older, you can contribute an additional $7,500 per year (called a catch-up contribution), for a total of $31,000.

These limits explore to your own contributions only. Your employer's match does not count toward your limit, but it does count toward a separate combined limit of $69,000 per year (for 2024). That combined limit includes your contributions, your employer's match, and any employer profit-sharing contributions.

The limits change each year based on inflation. Your plan administrator or payroll department can tell you the current year's limit.

When you can withdraw pre-tax 401(k) money

You can withdraw pre-tax 401(k) money without penalty once you reach age 59½. Before that age, withdrawals are subject to a 10 percent early withdrawal penalty plus income tax on the amount withdrawn.

A few exceptions exist. You can withdraw without the 10 percent penalty if you separate from service (leave your job) in the year you turn 55 or later, if you have a serious financial hardship that meets IRS rules, or if you become disabled. Hardship withdrawals are rare and require proof that you have no other way to pay for the expense. Even then, you still owe income tax on the withdrawal.

Some plans allow loans against your 401(k) balance. You borrow from your own account and repay yourself with interest. Loans do not trigger the 10 percent penalty, but if you leave your job before repaying the loan, the unpaid balance is treated as a withdrawal and subject to tax and penalty.

Pre-tax 401(k) and your tax return

Your pre-tax 401(k) contributions appear on your W-2 form in Box 1 as a reduction to your wages. You do not have to do anything special on your tax return — the reduction is already built in. Your taxable income is automatically lower because of the contribution.

When you withdraw money in retirement, those withdrawals are reported on a 1099-R form, and you report them as income on your tax return. At that point, you pay income tax on the full withdrawal amount.

Frequently Asked Questions

Does a pre-tax 401(k) contribution reduce my Social Security and Medicare taxes?

No. Pre-tax 401(k) contributions reduce federal income tax and state income tax, but you still pay Social Security tax (6.2 percent) and Medicare tax (1.45 percent) on the full amount of your salary. Your employer pays a matching amount of these taxes as well.

Can I change from pre-tax to Roth 401(k) mid-year?

Yes. Most plans allow you to change your election at any time, and the change takes effect on your next paycheck. You can also split future contributions between pre-tax and Roth. Money already in a pre-tax 401(k) stays pre-tax unless you convert it, which is a separate transaction that triggers taxes.

What happens to my pre-tax 401(k) if I leave my job?

The money stays in the account and continues to grow. You can leave it there if your balance is above $5,000 (some plans allow smaller balances to stay). You can also roll it into a new employer's 401(k) plan or into a traditional IRA. A rollover does not trigger taxes or penalties as long as the money moves directly from one account to the other.

Is there an income limit for pre-tax 401(k) contributions?

No. Unlike traditional IRAs, which have income limits for tax deductions, 401(k) plans do not. Anyone with earned income can contribute to a pre-tax 401(k) up to the annual limit, regardless of how much they earn.

Do I have to take required minimum distributions from a pre-tax 401(k)?

Yes. Starting at age 73, you must withdraw a minimum amount each year based on your age and account balance. The IRS calculates the amount using life expectancy tables. If you do not take the required amount, you owe a 25 percent penalty on the shortfall (reduced to 10 percent if corrected within two years).