How 401(k) Pretax Contributions Work

Yes, most 401(k) contributions are pretax

When you contribute to a traditional 401(k), the money comes out of your paycheck before federal income tax is calculated. Your employer reduces your gross pay by the amount you contribute, which lowers the income your employer reports to the IRS. You do not pay income tax on that money until you withdraw it in retirement.

This is different from a Roth 401(k), where contributions come out after tax. The choice between pretax and Roth depends on whether you want to reduce your taxes now or in retirement — a decision that depends on your current tax bracket and what you expect to earn later.

Key Takeaways

• Pretax 401(k) contributions lower your taxable income in the year you contribute, which means a smaller tax bill right now.
• You pay income tax on pretax contributions and all their growth when you withdraw the money in retirement.
• Roth 401(k) contributions are made with after-tax dollars, but withdrawals in retirement are tax-free.
• Many employers offer both pretax and Roth options, and you can split your contributions between them if your plan allows.
• Social Security and Medicare taxes (FICA) are still taken out of pretax 401(k) contributions.

How pretax contributions reduce your taxes this year

When you elect to contribute pretax money to your 401(k), your employer subtracts that amount from your gross pay before calculating federal income tax withholding. If you earn $50,000 a year and contribute $7,000 pretax, your employer reports only $43,000 as your taxable income to the IRS.

This means your federal income tax is calculated on $43,000, not $50,000. Depending on your tax bracket, that can save you hundreds of dollars in taxes in the current year. The lower your taxable income, the less you owe in federal income tax.

However, pretax contributions do not reduce Social Security and Medicare taxes. Those taxes (called FICA) are still taken from your full gross pay, even the portion you contribute to a 401(k).

What happens to pretax contributions in retirement

The tax you avoided now becomes due when you withdraw money from your pretax 401(k) in retirement. Every dollar you withdraw is treated as ordinary income and taxed at your current tax rate. If you withdraw $40,000 in a year when you are retired, that $40,000 counts as income on your tax return for that year.

This includes not only the money you contributed, but also all the growth and investment earnings inside the account. If you contributed $100,000 over your working years and it grew to $300,000, you pay income tax on the full $300,000 as you withdraw it.

You must begin withdrawals at age 73 (as of 2023, though this age changes under current law). The IRS requires you to take a minimum distribution each year, and that distribution is fully taxable.

Pretax versus Roth: the main difference

A Roth 401(k) works the opposite way. You contribute after-tax dollars — money that has already had income tax taken out — but your withdrawals in retirement are completely tax-free. The growth inside a Roth 401(k) is also never taxed.

The choice between pretax and Roth depends on your situation. Pretax is often better if you are in a high tax bracket now and expect to be in a lower bracket in retirement. Roth is often better if you are in a low bracket now and expect to earn more (and pay higher taxes) later. Many people split contributions between both types if their employer plan allows it.

Unlike a Roth IRA, there is no income limit to contribute to a Roth 401(k). Anyone whose employer offers one can use it, regardless of how much they earn.

How to choose pretax or Roth for your contributions

When you enroll in your employer's 401(k) plan, you will see options for contribution type. You choose what percentage of your paycheck goes to pretax, what percentage goes to Roth (if available), and what percentage stays as take-home pay. Most plans let you change this election once a year during open enrollment, or when you have a life event like a marriage or job change.

If you are unsure which is better for you, a tax professional or financial advisor can look at your specific income, tax bracket, and retirement goals. The IRS also publishes worksheets to help you estimate the difference.

Some employers match your contributions. Employer matches always go into the pretax side of your account, regardless of whether you chose pretax or Roth for your own contributions.

Common confusion about pretax 401(k)s

A frequent misunderstanding is that pretax contributions mean you never pay tax on that money. That is not true — you straightforward delay the tax until retirement. The IRS will collect it eventually, either as you withdraw or through required minimum distributions.

Another confusion is thinking that pretax contributions avoid all payroll taxes. They do not. Social Security and Medicare taxes are still withheld from pretax 401(k) contributions. Only federal income tax is reduced by the pretax election.

Some people also believe that pretax contributions lower their Social Security benefits. They do not. Social Security benefits are based on your earnings record, which includes the full amount you earned before any 401(k) contribution.

What happens if you withdraw pretax money early

If you withdraw pretax 401(k) money before age 59½, you owe income tax on the withdrawal plus a 10 percent early withdrawal penalty — unless an exception applies. Common exceptions include disability, a series of equal payments over your lifetime, or certain hardships (though hardship rules are strict and vary by plan).

This is one reason pretax contributions are meant for long-term retirement savings. The tax and penalty can take a large bite out of your money if you need it before retirement age.

Frequently Asked Questions

Can I change from pretax to Roth contributions mid-year?

Most plans let you change your contribution type during open enrollment, which is usually once a year. Some plans also let you change after a life event like marriage, divorce, or a change in employment. You cannot change the tax treatment of money already contributed, but you can change what happens with future paychecks.

Does my employer match count as pretax?

Yes. Employer matching contributions always go into the pretax side of your 401(k), even if you chose Roth for your own contributions. The match is not taxed until you withdraw it in retirement.

What if I leave my job — do I still owe taxes on pretax 401(k) money?

Not when ready. Your pretax 401(k) balance stays in the account (or rolls into an IRA or new employer plan) and is not taxed until you withdraw it. You can leave it there, roll it over, or take a distribution whenever you choose, subject to age and other rules.

Is pretax or Roth better if I am self-employed?

Self-employed people typically use a Solo 401(k) or SEP IRA instead of an employer plan. Both offer pretax options. A tax professional can help you decide based on your income and retirement timeline, since self-employed tax situations are more complex than W-2 employee situations.

Do pretax 401(k) contributions lower my taxable income for state taxes?

Most states follow federal rules and allow pretax 401(k) contributions to reduce state taxable income. However, a few states have different rules. Check your state's tax agency website or ask your employer's benefits team about your specific state.