If your employer offers a 401(k) and you’re not taking full advantage of it, you’re leaving one of the most powerful wealth-building tools in personal finance on the table. Yet millions of employees either don’t enroll, don’t contribute enough to get the employer match, or invest their contributions in the wrong funds.
This guide explains exactly how the 401(k) works, what decisions you need to make, and how to get the most out of yours.
What Is a 401(k)?
A 401(k) is an employer-sponsored retirement savings plan that allows you to contribute a portion of each paycheck to a tax-advantaged investment account. The name comes from the section of the tax code that governs it.
Contributions are made directly from your paycheck before you receive it — which means they come out of your gross pay, before taxes (for traditional contributions), making the impact on your take-home pay smaller than the contribution amount suggests. Contributing $200/paycheck to a 401(k) might only reduce your take-home by $150, because you’re saving on the taxes you would have owed on that $200.
Traditional vs. Roth 401(k)
Many employers now offer both options:
Traditional 401(k): Contributions are pre-tax — they reduce your taxable income now. You pay income tax when you withdraw the money in retirement.
Roth 401(k): Contributions are after-tax — no current tax break. But growth and qualified withdrawals in retirement are completely tax-free. No income limits apply (unlike the Roth IRA).
The choice follows the same logic as Roth vs. Traditional IRA: if you’re in a lower tax bracket now than you expect in retirement, favor Roth. If you’re in a high bracket now and expect lower in retirement, favor traditional.
Employer Match: Free Money You Can’t Afford to Miss
Many employers match employee contributions up to a certain percentage. A common structure: the employer matches 50 cents for every dollar you contribute, up to 6% of your salary. If you earn $60,000 and contribute 6%, that’s $3,600 from you and $1,800 free from your employer — a 50% instant return before any investment growth.
Not contributing enough to get the full match is one of the most costly financial mistakes employees make. Always — always — contribute at least enough to capture the full match before allocating money to any other savings or investment goal.
Note: most employers have a “vesting schedule” — you may need to stay employed for 2–5 years before the employer’s contributions are fully yours. Check your plan documents.
Contribution Limits
For 2026, the employee contribution limit is $23,500. If you’re 50 or older, you can contribute an additional $7,500 in “catch-up” contributions for a total of $31,000. These limits are per person — they apply to all 401(k) plans you participate in across all employers.
If maxing out isn’t immediately possible, work toward it gradually. Increasing your contribution by 1% each year (especially when you receive raises) is a proven path to getting there without feeling the impact on take-home pay.
How to Choose Your Investments
This is where many 401(k) participants feel overwhelmed — and where poor decisions can cost tens of thousands of dollars over a career.
Look for index funds. Most quality 401(k) plans include low-cost index funds that track the S&P 500, US total market, or international markets. These should be your first choice over actively managed funds.
Check the expense ratio. This is the annual fee charged by a fund, expressed as a percentage of assets. Look for funds with expense ratios below 0.20%. An expense ratio of 1% vs. 0.05% on a $100,000 portfolio costs roughly $950 extra per year — and far more over time as the balance grows.
Consider target-date funds. These “set it and forget it” funds automatically adjust their stock/bond allocation as you approach your target retirement year. They’re not always the cheapest option, but they’re often the best choice for employees who don’t want to manage their own allocation.
Avoid company stock concentration. If your employer offers its own stock in your 401(k), keep the allocation modest. Concentrating retirement savings in a single company — especially your employer — is a significant risk.
What Happens When You Leave a Job
You have several options when you leave an employer:
- Roll over to your new employer’s 401(k): Consolidates accounts, continues tax-advantaged growth
- Roll over to an IRA: More investment options and potentially lower fees; the preferred choice for many
- Leave it in your old employer’s plan: Acceptable if the plan has excellent investment options
- Cash out: Strongly inadvisable — you’ll owe income tax plus a 10% penalty, and you’ll lose all future compound growth on those dollars
Common 401(k) Mistakes to Avoid
- Not enrolling (many plans now auto-enroll — check that you’re opted in)
- Contributing less than the employer match amount
- Choosing high-fee funds when low-fee alternatives are available
- Never rebalancing your portfolio as it drifts from target allocation
- Cashing out when changing jobs
- Not increasing contributions as income grows
Your 401(k) is likely to be one of the largest assets you ever own. Treating it with intentionality — from enrollment through investment selection to rollover decisions — is one of the highest-return activities in your financial life.
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