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How a 401(k) works (and why most people leave money on the table)
A 401(k) is the most powerful wealth-building tool most American workers will ever touch — and also the one most often left half-used. Here is how it actually works in 2026, why the employer match is free money you should never skip, and how to choose between Traditional and Roth.
How a 401(k) actually works
A 401(k) is a retirement account offered through your employer. Money comes out of your paycheck automatically and goes straight into investments you choose — usually low-cost index funds or a target-date fund that gets more conservative as you near retirement.
The magic is tax-advantaged, compounding growth. You are not taxed on the gains every year, so your balance grows on top of itself decade after decade. Starting early matters far more than picking the perfect fund: a dollar invested at 30 has 35 years to multiply.
2026 contribution limits
In 2026 you can contribute up to $24,500 of your own salary — the elective deferral limit set by the IRS. If you are 50 or older, you can add an $8,000 catch-up, for $32,500 total. A SECURE 2.0 super catch-up lets workers who turn 60 to 63 during the year add $11,250 instead, for $35,750.
Those numbers are just your own money. Counting employer contributions, total additions to your account can reach $72,000 in 2026. Separately, you can also fund an IRA up to $7,500 — the limits do not overlap.
Employer match types
The most common formula is a partial match: your employer adds 50 cents per dollar you contribute, up to 6% of your pay. Others offer a full match (100%) up to 3% to 5%, or a tiered formula such as 100% on the first 3% and 50% on the next 2%.
However it is structured, the match is part of your compensation. Contributing less than the match cap is the same as turning down a raise your employer already offered you.
Vesting schedules
The money you contribute is always 100% yours. Employer contributions may vest over time. With cliff vesting you own 0% until a set date — say three years — then jump to 100%. With graded vesting you earn it gradually, often 20% a year over five to six years.
If you leave before you are fully vested, you forfeit the unvested employer money. That is worth knowing before you change jobs: sometimes waiting a few months locks in thousands of dollars.
Roth 401(k) vs Traditional 401(k)
Traditional contributions are pre-tax: they lower your taxable income today, and you pay tax when you withdraw in retirement. Roth contributions are after-tax: no break today, but qualified withdrawals — including all the growth — are completely tax-free.
A simple rule of thumb: choose Traditional if you expect a lower tax bracket in retirement, and Roth if you expect the same or higher, or you simply want tax-free flexibility later. Note that the employer match always lands in a pre-tax (Traditional) bucket, no matter which you pick.
When to roll over
When you leave a job you have options: leave the money where it is, roll it into your new employer plan, or roll it into an IRA. Rolling to an IRA often unlocks more investment choices and lower fees.
Whatever you do, avoid cashing out. An early withdrawal before age 59½ usually triggers income tax plus a 10% penalty — a brutal price for money meant to compound for decades.
Frequently asked questions
- How much should I contribute to my 401(k)?
- At a minimum, contribute enough to capture the full employer match — that is free money. A common target is 10% to 15% of your income including the match. If that feels like a lot, start lower and raise your rate 1% every year.
- What happens to my 401(k) if I change jobs?
- Your vested balance is always yours. You can leave it in the old plan, roll it into your new employer plan, or roll it into an IRA. Avoid cashing out, which triggers taxes and an early-withdrawal penalty.
- Is the employer match really free money?
- Yes. If your employer matches 50% up to 6% and you earn $60,000, contributing 6% earns you an extra $1,800 a year you would otherwise leave behind. Over a career, that compounds into hundreds of thousands of dollars.
- Can I contribute to both a 401(k) and an IRA in 2026?
- Yes. The $24,500 401(k) limit and the $7,500 IRA limit are separate. At higher incomes, IRA deductibility and Roth IRA eligibility phase out, but you can still contribute to your 401(k) in full.
- What is the difference between the catch-up and super catch-up?
- If you are 50 or older you can add an $8,000 catch-up in 2026. If you turn 60, 61, 62, or 63 during the year, a SECURE 2.0 super catch-up lets you add $11,250 instead.
- Are 401(k) withdrawals taxed?
- Traditional withdrawals are taxed as ordinary income. Qualified Roth withdrawals are tax-free. In both cases, withdrawing before age 59½ usually adds a 10% penalty.