The 401(k) offers a tax deduction, employer matching, and decades of tax-deferred growth. It is objectively the best wealth-building tool most Americans have access to. Most people are fumbling it.
Mistake #1: Not Getting the Full Match
If your employer matches 4% and you contribute 3%, you leave 1% of your salary — pure free money — on the table annually. This is the only guaranteed 100% return in investing. If you cannot afford to contribute enough to capture the full match, reduce other spending first. Nothing else in your financial life has a better return.
Mistake #2: Keeping the Default Investment
Most 401(k) auto-enrollments put you in a conservative money market or stable value fund — which barely beats inflation. Check what you're actually invested in. If you're under 50, you likely want significantly more equity exposure. A target-date fund matching your retirement year is a safe default if your plan has one.
Mistake #3: Paying High Expense Ratios
Many 401(k) plans offer expensive actively managed funds alongside cheap index funds. Check expense ratios. Anything above 0.5% is suspect. Anything above 1% is robbing you. If your plan only offers expensive funds, contribute enough for the match, then invest the rest in an IRA where you control the fund selection.
Mistake #4: Cashing Out When You Leave a Job
The average American changes jobs 12 times. Each time, some people cash out their 401(k). This triggers income tax plus a 10% early withdrawal penalty. A $30,000 cash-out at age 35 might net you $18,000 after taxes — and cost you $280,000 in foregone compound growth by age 65. Roll it over to an IRA instead.
Mistake #5: Ignoring the Roth 401(k) Option
If your employer offers a Roth 401(k) and you're in a low-to-moderate tax bracket (under ~$150K household income), the Roth option is often the better choice. You pay taxes now at your current rate; growth and withdrawals are tax-free. In a higher future tax environment, this is extremely valuable.
Mistakes #6-8 in Brief
- #6: Taking loans from your 401(k) — Only in genuine emergencies. You pay it back with after-tax dollars and miss market returns while the money's out.
- #7: Not increasing contributions with raises — Every raise, bump your contribution rate by half the raise amount. You never feel it because you never had it.
- #8: Not reviewing beneficiary designations — Your 401(k) goes directly to whoever is named as beneficiary, regardless of your will. Review after every major life event.