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Your employer offers a 401k and even matches contributions. You've been ignoring it because it feels complicated. That match is free money — and every year you don't take it, you're handing it back. This guide explains exactly how 401k works, how much you should contribute, and what the 2026 rules mean for your wallet.
What Is a 401k?
A 401k is a tax-advantaged retirement savings plan offered by employers in the United States. You contribute a percentage of your salary before income tax is calculated — which means every dollar you put in reduces your taxable income for that year. The money grows in investments (usually mutual funds or ETFs) and you pay tax only when you withdraw it in retirement.
The name comes from the section of the US tax code that created it: section 401(k) of the Internal Revenue Code.
2026 401k Contribution Limits (IRS)
Employee limit: $23,500 | Catch-up (age 50+): additional $7,500 | Total with employer: $70,000
How Does the Employer Match Work?
An employer match is the most powerful feature of a 401k. If your employer offers a 100% match up to 3% of salary, it means: you contribute 3%, they add 3% — effectively doubling your contribution at no extra cost to you.
| Salary | Your Contribution (3%) | Employer Match (3%) | Total Going In |
|---|---|---|---|
| $50,000 | $1,500/year | $1,500/year | $3,000/year |
| $70,000 | $2,100/year | $2,100/year | $4,200/year |
| $90,000 | $2,700/year | $2,700/year | $5,400/year |
| $120,000 | $3,600/year | $3,600/year | $7,200/year |
Not contributing at least enough to get the full employer match is one of the most expensive financial mistakes American workers make. You are walking away from a guaranteed 100% return on that money before it even gets invested.
Traditional 401k vs Roth 401k — Which Should You Choose?
Many employers now offer both options. The difference comes down to when you pay tax:
| Traditional 401k | Roth 401k | |
|---|---|---|
| Contributions | Pre-tax (reduces income now) | After-tax (no immediate saving) |
| Withdrawals in retirement | Taxed as ordinary income | Tax-free |
| Best for | Higher earners now, lower tax in retirement | Lower earners now, higher tax later |
| 2026 limit | $23,500 combined | $23,500 combined |
The practical rule: if you expect to be in a higher tax bracket in retirement than you are now, choose Roth. If you expect to be in a lower bracket in retirement, choose Traditional. When unsure — and most people are — splitting contributions between both hedges your tax risk.
How Much Should You Actually Contribute?
There is a clear priority order for contributions:
Step 1 — Contribute at least enough to get the full employer match. This is non-negotiable. Whatever percentage unlocks the full match — contribute that. Always.
Step 2 — Max out an IRA if eligible. After the match, contribute up to $7,000 to a Roth or Traditional IRA (2026 limit) before adding more to your 401k. IRAs often have better investment choices at lower fees.
Step 3 — Increase 401k contributions toward the $23,500 limit. Once your IRA is maxed, continue increasing your 401k contributions until you hit the annual limit or your budget ceiling.
What Happens to Your 401k When You Change Jobs?
Your 401k contributions are always yours. Employer contributions vest over time — meaning you may need to stay employed for 1–6 years before you own the matched funds fully. The most common vesting schedules are:
| Years Employed | Cliff Vesting (common) | Graded Vesting (common) |
|---|---|---|
| Year 1 | 0% | 0–20% |
| Year 2 | 0% | 40% |
| Year 3 | 100% | 60% |
| Year 4 | 100% | 80% |
| Year 5+ | 100% | 100% |
When you leave a job, you can roll your 401k into your new employer's plan or into an IRA. Avoid withdrawing the money — early withdrawals before age 59½ incur a 10% penalty plus income tax, which can wipe out a quarter or more of your savings immediately.
The Power of Starting Early — Real Numbers
Someone who contributes $500 per month starting at age 25 versus age 35, assuming 7% average annual returns:
| Starts at 25 | Starts at 35 | |
|---|---|---|
| Monthly contribution | $500 | $500 |
| Total contributed | $240,000 | $180,000 |
| Balance at 65 | $1,310,000 | $567,000 |
| Cost of the 10-year delay | — | $743,000 less |
The 10-year delay costs $743,000 in retirement savings despite only $60,000 less being contributed. That gap is compound interest — and it works against you the longer you wait.