How a 401(k) Works, and Why the Employer Match Matters

What is a 401(k)?

A 401(k) is a retirement account you fill straight from your paycheck, through your employer. With a traditional 401(k), the money goes in before income tax, so saving $100 lowers your take-home pay by less than $100. Many employers also add money of their own, called a match. And the money is invested, so it can grow for decades before you need it.

I've been saving for retirement since my very first job. That job didn't offer a 401(k), but it had a different retirement account that came out of every paycheck automatically, and I put money in from day one. Once a 401(k) was available to me, I signed up right away. Even so, knowing what I know now about compound interest, I'd have started even sooner if I could have.

Picture a tank with its own pipe

In the paycheck post, your pay is water running from the main through a row of filters to your faucet. Some filters send water to the government (taxes). Others send it to your own tanks, where it isn't gone, just stored for later.

A 401(k) is one of those tanks, and its pipe is special: it branches off before the income tax filter. Water that goes into the tank never passes through that filter on the way in, so:

• The tank fills faster than your faucet slows down. Every dollar you send there is a full dollar in the tank, but it only costs you the part that would have made it through the tax filter.
• Your employer may pour in water of its own. That's the match, and it's the part people most often leave on the table.
• The water in the tank is invested. It isn't sitting still; it's working, and over decades it can snowball.

The catch: the tank is meant for retirement. Water you take out before then usually costs extra (more on that below).

How much does $100 into a 401(k) really cost?

Start with round numbers. Say your top tax bracket is 12% and your state takes a flat 5%. If you didn't save that $100, the tax filters would take about $17 of it, and $83 would reach your faucet.

Send it to your 401(k) instead, and the whole $100 goes into your tank, while your take-home pay drops by only about $83. The other $17 is income tax you don't pay now.

The higher your bracket, the bigger the break: in the 22% bracket with the same state tax, $100 into the tank costs you about $73. (Social Security and Medicare still come out of 401(k) money, so the break is on income tax only. Your top bucket and your 401(k) shows why it's your top rate that counts.)

A real paycheck, with and without a 401(k)

Now real numbers. Here's the paycheck from the paycheck post: a $60,000 salary, paid every two weeks (26 paychecks of $2,307.69), a single filer, $75 a paycheck for health insurance, and a made-up flat 5% state tax, using 2026 federal figures.

	No 401(k)	5% into a traditional 401(k)
Into your 401(k) each paycheck	$0	$115.38
Federal income tax	$184.08	$170.23
State income tax	$111.63	$105.87
Take-home pay	$1,766.18	$1,670.41
Into your 401(k) for the year	$0	$3,000
Take-home pay for the year	$45,920.68	$43,430.68

Putting $3,000 a year into the tank shrinks take-home pay by only $2,490. The other $510 is income tax you didn't pay this year. The math is simplified (each tax is figured for the year and split evenly across paychecks), so a real pay stub may differ a little.

Try your own numbers. The calculator starts on this example with 2026 figures; change the 401(k) percent and watch take-home pay move by less than the 401(k) amount. The paycheck calculator uses this year's figures.

What is an employer match?

An employer match is money your employer puts into your 401(k) when you put money in. It's part of your pay, but you only get it if you contribute.

Every plan sets its own formula, and a few common shapes look like this:

• Dollar for dollar up to a percent of your pay: you put in 5%, they put in 5%.
• Fifty cents on the dollar up to a percent: you put in 6%, they put in 3%.
• No match at all. Some employers don't offer one, and a 401(k) can still be worth it for the tax break.

The number to find is how much you have to put in to get the full match. Put in less, and you're turning down part of your pay. Your plan's summary or your benefits site will spell out the formula.

My own rule: I always put in at least enough to get the full match. It's essentially free money.

Vesting is the other thing to check. The money you put in is always yours. Your employer's match may vest over time instead, meaning it becomes fully yours only after you've worked there long enough, often a few years. Leave before then and you may keep only part of it. The IRS explains vesting (opens in a new tab), and your plan lists its own schedule.

What's the match worth over 30 years?

Go back to the $60,000 example and add a dollar-for-dollar match up to 5%. You put in $3,000 a year, and your employer adds another $3,000. That's $6,000 a year in your tank, for the same $2,490 of take-home pay.

Now let it grow. At a 7% yearly return (an example, not a promise; what rate will you actually get? explains why) for 30 years:

• Without the match: $250 a month grows to $283,382.36. You put in $90,000.
• With the match: $500 a month grows to $566,764.72. You put in the same $90,000; your employer put in the other $90,000.

The match doesn't just add $90,000. Because that money grows too, it doubles the ending balance. These calculators add a year's contributions once a year and assume the same return every year; real markets go up and down, and your balance will too.

Traditional or Roth 401(k)?

Many plans offer two kinds of 401(k). The difference is when you pay income tax:

	Traditional 401(k)	Roth 401(k)
Going in	Before income tax, so it lowers your taxes now	After income tax, so no break now
Coming out in retirement	Taxed as income	Tax-free, if you follow the rules
Tends to fit when	You expect a lower tax rate in retirement than now	You expect the same or a higher rate in retirement

In the water picture, a traditional 401(k) skips the tax filter on the way into the tank and passes through it on the way out. A Roth passes through it on the way in, and the water (including everything it grew into) comes out untaxed.

Nobody knows their future tax rate for sure, which is why some people split their savings between the two. I use a traditional 401(k). Employer matches have usually gone in as traditional money, even when you choose Roth. The IRS compares the two (opens in a new tab) in detail. This is educational, not financial advice; for a choice this personal, consider talking with a tax professional or financial planner.

How much can you put in a 401(k)?

You can put in up to a yearly limit set by the IRS, which usually rises a little each year, plus an extra catch-up amount from age 50. Your employer's match doesn't count against your limit. The IRS lists the current limits (opens in a new tab).

Most people aren't close to the limit, and that's fine. I'm not either: I put in enough to get the full match, and that's where my 401(k) stops.

What comes after the match?

Past the match, I don't think there's one right answer; it depends on your situation. Two options I'd look at:

• A Roth IRA: an individual retirement account you open yourself, with after-tax money that can come out tax-free in retirement.
• A regular brokerage account: no tax break, but you can get at the money before retirement without the extra 10% tax a 401(k) usually charges (see the next section).

You can also put more into your 401(k), up to the limit. This is educational, not financial advice; where your extra savings should go depends on your goals and your taxes.

Can you take money out of a 401(k) early?

You can, but it usually costs you. Money taken out before age 59½ is generally taxed as income and hit with an extra 10% tax, according to the IRS (opens in a new tab), which also lists the exceptions. Some plans let you borrow from your own 401(k) instead, with rules about paying it back.

That's why the tank works best for money you won't need for a long time. For surprises like a car repair or a few months between jobs, an emergency fund in a regular savings account is the better tank: there's no penalty to get at it.

I've had a stretch like that myself, when I was changing jobs and life got complicated. I'd set money aside ahead of time, and that's what kept it from turning into a crisis.

It's also OK to turn your 401(k) down for a while when life happens. During that same stretch, I needed my whole paycheck, so for a while I didn't put in enough to get the full match. What matters is turning it back up once things settle down.

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

Your money stays yours, including any match that's vested. You can usually:

• Leave it in your old employer's plan, if the plan allows it.
• Roll it over into your new employer's 401(k), or into an IRA (an individual retirement account you open yourself).
• Cash it out. This counts as taking it out early, with the taxes and the 10% extra tax above, and it drains the tank you've been filling.

A direct rollover moves the money from one tank straight into another of the same kind (traditional to traditional, Roth to Roth) without taxes. Follow your plan's instructions so it counts as one. Moving pre-tax money into a Roth IRA is different: it's a Roth conversion, and the amount you move is taxed as income that year.

When I've changed jobs, I've rolled my old retirement accounts into IRAs of my own, a traditional IRA or a Roth IRA.

Why it matters

Retirement is always on my list, even through the stretch when I had to turn it down. I'm also saving for my daughter's college in a 529 plan, and for shorter-term goals in savings buckets of their own. But a 401(k) is the one place where the tax break, the match, and decades of growth all stack up, and it fills automatically, a little each paycheck, without me having to remember.

That's "pay yourself first" on autopilot: the money is split off in payroll before it ever reaches your faucet. It's my best practical tip for any kind of saving. Have your payroll send a percentage straight to savings or investments, and you never have to think about it.

In my 20s, I turned saving into a game. I tracked my savings rate (the share of my income I saved each month) and pushed it as high as I could, at one point to 40%. I kept Networthify's early retirement calculator (opens in a new tab) bookmarked, which projects your retirement date from your savings rate, and I was cutting expenses and investing aggressively to reach financial independence sooner.

It also fits right into your cash flow: the money comes out before your take-home pay, so you plan your spending around what reaches your faucet, and saving happens on its own.

What to take with you

• Find your match formula on your benefits site, and the percent you need to put in to get all of it.
• Check your current percent on your last pay stub. If it's below the full match, raising it is usually the first move.
• Remember the tax break: with a traditional 401(k), $100 into your tank costs you less than $100 of take-home pay.
• Look up your vesting schedule before you change jobs, so you know how much of the match you keep.
• Leave the tank alone until retirement when you can. Early withdrawals usually cost an extra 10% on top of income tax.
• Get the full match, then decide where extra savings go: more in your 401(k), a Roth IRA, or a regular brokerage account.
• Pay yourself first. Let payroll send your savings out before your take-home pay, and let compound interest do the rest.

Want to see what your own 401(k) percent does to your paycheck? Try the paycheck calculator, or see how your savings could grow with the compound interest calculator.