401(k) Basics: How It Works and How the Match Works
By the TidyTally team · Last updated October 21, 2026
A 401(k) is a retirement account offered through your employer, and for many people it is the biggest wealth-building tool they will ever use. Contributions come directly out of your paycheck, many employers add free money through a match, and the money grows tax-advantaged. Here is how it works, what the numbers mean, and the mistakes to avoid.
How a 401(k) works
You choose a percentage of your pay to contribute and the money is deducted automatically each pay period and invested in funds chosen from your plan's menu. With a traditional (pre-tax) 401(k), contributions lower your taxable income now, and you pay income tax on withdrawals in retirement. With a Roth 401(k), if offered, you contribute after-tax dollars and qualified withdrawals are tax-free. Many plans offer both, and you can split between them. The same pre-tax versus after-tax reasoning from our Roth vs. Traditional IRA guide applies.
2026 contribution limits
For 2026, employees can contribute up to $24,500 to a 401(k), up from $23,500 in 2025. Workers age 50 and older can add a catch-up contribution of $8,000. These limits apply to your own contributions across all 401(k) plans; employer contributions are counted separately under a higher overall limit. Check the IRS site for the latest figures, which are adjusted periodically.
The employer match: free money
Many employers match a portion of what you contribute. A typical formula is "50% of the first 6% of pay." On an $80,000 salary, if you contribute 6% ($4,800), the employer adds 50% of that, or $2,400. If you contribute only 3%, you get just $1,200 of match and leave $1,200 on the table.
Matching formulas vary, so read your plan's summary. The rule of thumb that most financial educators agree on: contribute at least enough to earn the full match, because it is an immediate, guaranteed return that no investment can reliably beat. Try different contribution levels in the Retirement Savings Calculator to see the long-term effect.
Vesting: when the match becomes yours
Your own contributions are always yours. Employer contributions may be subject to a vesting schedule, meaning you earn full ownership over time — for example, 20% per year over five years (graded) or 100% after three years (cliff). If you leave before you are fully vested, you may forfeit part of the match. Check your plan before changing jobs.
Investments and fees
Most plans offer a menu of mutual funds or index funds, and often target-date funds that gradually shift from stocks to bonds as you approach a chosen retirement year. Fees matter: a fund's expense ratio is deducted from your returns every year, and small differences compound into large sums over decades. Compare funds on cost as well as performance, and review plan administration fees in your annual disclosure. The Compound Interest Calculator shows how growth builds over time.
Changing jobs and early withdrawals
When you leave an employer, you can usually leave the money in the old plan, roll it into your new employer's plan, or roll it to an IRA. A direct rollover avoids taxes and penalties. Cashing out is expensive: you generally owe income tax plus a 10% early-withdrawal penalty if under 59½, and you lose years of compounding. Some plans allow loans against your balance, which can be risky if you leave your job with an outstanding loan.
A simple 401(k) plan
Enroll as early as possible, contribute at least enough to capture the full match, raise your contribution by 1% each year or with every raise, choose a diversified low-cost option such as a target-date or index fund, and avoid tapping it early. Then see how much you need overall in our guide on how much to save for retirement.
Frequently asked questions
What is the 401(k) contribution limit for 2026?
The employee deferral limit is $24,500 for 2026, with an additional $8,000 catch-up contribution for workers age 50 and older.
Should I contribute to a 401(k) or pay off debt first?
Many people contribute enough to get any employer match first, since it is an immediate return, then prioritize high-interest debt such as credit cards, and then increase retirement savings. Your situation may call for a different balance.
What happens to my 401(k) if I quit?
The money remains yours (subject to vesting for employer contributions). You can leave it in the plan, roll it over to a new plan or an IRA, or cash out — which usually triggers taxes and possibly a penalty.
Is a Roth 401(k) better than a traditional 401(k)?
It depends on whether you expect to be in a higher or lower tax bracket in retirement than now. Roth contributions give tax-free withdrawals later; traditional contributions give a tax break now.