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DDonnie · Personal Finance Expertupdated Nov 9, 2026

401k: How Does It Actually Work?

Key takeaways
  • The 401k is a retirement account your employer sets up: part of your paycheck goes into it every payday, before tax (except in a Roth 401k).[1]
  • In 2026, you can contribute up to $24,500 a year, and up to $32,500 from age 50.[2]
  • Example: you invest $500 a month from age 35 to 65. At 5% a year, your 401k will be worth about $399,000. If you withdraw 4% a year, it pays you about $1,330 a month.
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The 401k at a glance
TopicWhat you need to know
Who sets it upyour employer, which also picks the list of funds offered [3]
What you can contribute in 2026$24,500 a year, $32,500 from age 50, $35,750 from age 60 to 63 [2]
Limit including your employer's money$72,000 a year in 2026 [2]
TaxTraditional 401k: less tax today, tax on withdrawals. Roth 401k: tax today, tax-free withdrawals [4]
Withdrawal before age 59½10% extra tax, with some exceptions [5]
Example balance$500 a month from age 35 to 65, at 5% a year: about $399,000
1

What is a 401k?

The 401k is a retirement account your employer sets up: part of your paycheck goes into it every payday.[1]

  • The money leaves before it reaches your checking account: you earn $5,000 a month and choose 10%, so $500 goes into your 401k each month.
  • Your money is invested in funds, chosen from the list your plan offers.[3]
  • What you contribute always stays 100% yours, even if you leave your employer.[6]
  • Your employer can add money to your account.[1]
2

How a 401k works, in 4 steps

A 401k works in 4 steps, from your paycheck to your retirement.

  1. You choose how much to contributeYou choose a percentage of your salary, for example 10%. Some plans enroll you automatically, at a percentage set by your employer.[7]
  2. Your employer can add to itExample: your employer adds 50 cents for every dollar you contribute.[7] On your $500 for the month, your employer adds $250.
  3. You pick your funds from the plan's listYour account grows with the gains of the funds you pick, and shrinks with their losses.[8]
  4. You get your money back in retirementStarting at age 59½, you withdraw your money with no extra tax.[5]
3

The 3 advantages of a 401k

A 401k has three advantages: less tax today, the money your employer adds, and automatic saving.

  • Less tax today: your traditional contributions are taken out of your taxable income.[1] Example: your federal tax bracket, the rate applied to the last dollars you earn, is 22%.[9] Your $500 contribution only lowers your take-home pay by about $390 ($500 minus $110 in tax).
  • Your employer's money: at 50 cents per dollar, your $500 becomes $750 every month.[7] From age 35 to 65, at 5% a year, your 401k reaches about $598,000 instead of $399,000.
  • Effortless saving: the money leaves before it reaches your checking account. So that money never passes through your hands.
The word to know
Employer match : The money your employer adds to your 401k when you contribute. Example: at 50 cents per dollar, $100 contributed becomes $150.
Watch outThe money your employer adds may only become truly yours after a few years of work. Example: with a 3-year rule, you lose that money if you leave before then.[6]
4

Traditional 401k or Roth 401k: when do you pay the tax?

Choosing between a traditional 401k and a Roth 401k means deciding when you pay the tax: now or in retirement.[4]

  • Traditional 401k: you contribute before tax, then you pay tax on your withdrawals.[4]
  • Roth 401k, if your plan offers it: you contribute after tax, and your withdrawals are tax-free.[4] To withdraw tax-free, your Roth 401k must be at least 5 years old, and you must be at least 59½, except in case of disability or death.[4]
  • A Roth 401k never forces you to withdraw during your lifetime.[10]
  • Simple rule: if your tax rate drops in retirement, the traditional 401k makes you pay less tax. If your rate goes up, the Roth 401k makes you pay less tax.
  • Example: $1,000 contributed to a traditional 401k saves you $220 in tax today at a 22% rate. If you withdraw that $1,000 in retirement at a 12% rate, you pay $120 in tax.
5

How much should you contribute to your 401k in 2026?

In 2026, you can contribute up to $24,500 a year of your salary to your 401k, and more from age 50.[2]

What you can contribute in 20262026 limit including your employer's moneyUnder 50$24,500$72,00050 to 59, or 64 and older$32,500$80,00060 to 63$35,750$83,250
  • The limit including your employer's money counts your contributions and theirs together.[2]
  • A good first goal: contribute at least enough to get your employer's full match. Otherwise, you give up money your employer would have paid you.
TipRaise your percentage by one point with every raise. Example: on $5,000 a month, going from 10% to 11% adds $50 a month to your 401k.
6

Withdrawing from your 401k: starting at age 59½

Before age 59½, a withdrawal costs 10% extra tax, with some exceptions.[5]

  • Example: you withdraw $10,000 from your traditional 401k at age 40. You pay $1,000 in extra tax, then income tax on that $10,000.[5]
  • Leaving your job or disability: you don't pay the extra tax if you leave your employer in the year you turn 55 or later, or if you become totally and permanently disabled.[5]
  • Birth or adoption: you can withdraw up to $5,000 per child without the extra tax.[5]
  • Emergency: one withdrawal a year, up to $1,000, for an emergency expense also avoids the extra tax.[5]
  • Starting at age 73, you must withdraw a minimum amount each year. Your plan may let you wait until you retire if you're still working.[10]
7

401k or company pension: what's the difference?

A company pension promises you a fixed amount every month in retirement. A 401k promises no amount.[8]

  • Company pension: the amount is set in advance, for example based on your salary and years of work.[8]
  • 401k: your final balance depends on your contributions, plus or minus your investment gains.[8]
  • Example: a company pension promises you $2,000 a month for life. A 401k leaves you a balance, for example $399,000, that goes up or down with the markets.
  • The 401k is still a retirement plan: the U.S. Department of Labor classifies it as a defined contribution plan.[8]
The word to know
Defined contribution plan : A retirement plan where you know what you contribute, but not what you will get. Example: you contribute $500 a month, and your final balance depends on the markets.[8]
8

3 mistakes to avoid with your 401k

Three mistakes cost a lot with a 401k: ignoring fees, withdrawing too early, and cashing out your account when you change jobs.

  • Ignoring fees: 1% more in fees each year weighs heavily over 35 years.[3] Department of Labor example: $25,000 invested for 35 years at 7%, with no new contributions, grows to $227,000 with 0.5% in fees.[3] With 1.5% in fees, it grows to $163,000, or 28% less.[3]
  • Withdrawing before age 59½: you pay 10% extra tax, and the money you withdraw stops growing.[5]
  • Cashing out your 401k when you change jobs: on a check made out to you, the plan withholds 20%, and you have 60 days to put it all back.[11] Example: on $50,000, you receive $40,000, and you must find $10,000 elsewhere to put back the full $50,000.
  • Choose a direct transfer to another plan or an IRA, a retirement account you open yourself, without your employer: no tax is withheld.[11]
?

Your questions

Is a 401k an investment account?

Yes. Your money is invested in funds chosen from your plan's list, and its value goes up or down with them.[3]

How does a 401k help you prepare for retirement?

Your 401k pays the part of your retirement expenses that your public pension (Social Security) doesn't cover. Example: you spend $4,000 a month and your public pension pays $1,800: your 401k and your other investments must cover the missing $2,200.

What does “401k” mean?

“401k” comes from paragraph (k) of section 401 of the U.S. tax code: that paragraph sets the rules for this plan.[12]

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Sources

  1. 401(k) plans · Internal Revenue Service (IRS) · January 30, 2026
  2. Retirement topics: 401(k) and profit-sharing plan contribution limits · Internal Revenue Service (IRS) · April 8, 2026
  3. A Look at 401(k) Plan Fees · U.S. Department of Labor, Employee Benefits Security Administration (EBSA)
  4. Roth comparison chart · Internal Revenue Service (IRS) · September 4, 2026
  5. Retirement topics: Tax on early distributions · Internal Revenue Service (IRS) · December 11, 2025
  6. Retirement topics: Vesting · Internal Revenue Service (IRS) · April 8, 2026
  7. 401(k) plan overview · Internal Revenue Service (IRS) · August 4, 2026
  8. Types of Retirement Plans · U.S. Department of Labor
  9. IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill (IR-2025-103) · Internal Revenue Service (IRS) · October 9, 2025
  10. Retirement topics: Required minimum distributions (RMDs) · Internal Revenue Service (IRS) · April 8, 2026
  11. Rollovers of retirement plan and IRA distributions · Internal Revenue Service (IRS) · May 31, 2026
  12. 26 U.S.C. 401 – Qualified pension, profit-sharing, and stock bonus plans · U.S. Government Publishing Office (govinfo), United States Code · 2023 edition

This article is for education only. It is not investment advice: investing carries a risk of loss.

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