Common 401(k) Mistakes and How to Avoid Them

29 March 2026

Saving for retirement is one of the smartest financial moves you can make, and a 401(k) plan is a fantastic vehicle to help you get there. But let's be honest—401(k) rules can be complex, and it's easy to make mistakes that could cost you thousands (or even hundreds of thousands) of dollars over time.

Are you unknowingly sabotaging your retirement savings? Many people are, and the worst part is they don’t even realize it. Let’s break down the biggest 401(k) mistakes people make and, more importantly, how to avoid them.

1. Not Contributing Enough to Get the Employer Match

One of the biggest financial mistakes you can make is leaving free money on the table. Many employers offer a 401(k) match—meaning they’ll contribute a percentage of your salary to your retirement account if you do.

Why It’s a Mistake

If your employer offers a dollar-for-dollar match up to 5% of your salary and you only contribute 3%, you’re missing out on free money. That’s essentially turning down a bonus on your paycheck for no reason.

How to Avoid It

Always contribute at least enough to get the full employer match. If your budget is tight, start by cutting small expenses—like eating out or subscription services—to free up extra cash.

2. Delaying Contributions to Your 401(k)

The earlier you start contributing, the better. Many people think they’ll start saving "when they make more money," but time is your biggest asset when it comes to retirement savings.

Why It’s a Mistake

Thanks to compound interest, your money grows exponentially over time. The longer you wait, the more you’ll have to contribute later to catch up.

How to Avoid It

Start contributing as soon as you’re eligible, even if it’s just a small percentage of your paycheck. Over time, increase your contributions as your salary grows.

3. Not Increasing Contributions Over Time

Many people stick with the bare minimum contribution and never adjust it as they earn more.

Why It’s a Mistake

Inflation eats away at the value of money over time, which means the amount you’re saving today won’t have the same purchasing power in retirement. Plus, as you advance in your career, your expenses often rise, making it harder to catch up later.

How to Avoid It

Set a goal to increase your contributions by 1% every year or whenever you get a raise. Most 401(k) plans allow you to automate this process, so take advantage of it if possible.

4. Cashing Out When Changing Jobs

It’s tempting to take that lump sum when switching jobs, but doing so can seriously hurt your financial future.

Why It’s a Mistake

When you cash out your 401(k), three things happen:
1. You’ll owe income tax on the withdrawal.
2. If you're under 59½, you'll likely face a 10% early withdrawal penalty.
3. Most importantly, you lose future compound growth on that money.

How to Avoid It

Instead of cashing out, roll over your 401(k) into an IRA or your new employer’s 401(k) plan. This keeps your retirement money growing without penalties or taxes.

5. Ignoring Investment Choices

Many employees sign up for their 401(k), pick a default investment option, and never look at it again.

Why It’s a Mistake

Your investment choices determine how much your savings grow. If you’re too conservative (like keeping all your money in a money market fund), your returns may not even outpace inflation. On the other hand, if you're too aggressive, you might expose yourself to unnecessary risks.

How to Avoid It

Take time to understand your investment options. Most plans offer target-date funds, which automatically adjust your investment mix as you approach retirement. If you’re unsure, consult a financial advisor or use your plan’s risk assessment tools.

6. Paying High Fees

401(k) fees might not seem like a big deal now, but over 30–40 years, they can eat away at your retirement savings.

Why It’s a Mistake

Some funds charge high expense ratios and management fees, which reduce your total returns over time.

How to Avoid It

Review your plan's fee structure. If your 401(k) offers low-cost index funds, consider those instead of actively managed funds with high fees. Every percentage point you save in fees means more money in your pocket.

7. Taking a 401(k) Loan

Many people borrow from their 401(k) thinking it’s an easy way to get cash. While it is an option, it’s usually not a good one.

Why It’s a Mistake

- You’re borrowing from your future self, meaning you miss out on investment growth.
- If you leave your job before repaying the loan, you may have to pay it back in full within 60 days—or face heavy taxes and penalties.
- If you default, the loan becomes a taxable distribution.

How to Avoid It

Only consider a 401(k) loan as an absolute last resort. Explore other options, like a personal loan or home equity line of credit, before dipping into your retirement savings.

8. Not Rebalancing Your Portfolio

Over time, your investments may drift from your intended asset allocation due to market fluctuations.

Why It’s a Mistake

If you originally planned for a mix of 70% stocks and 30% bonds, but years of stock growth push it to 90% stocks and 10% bonds, you’re taking more risk than you intended.

How to Avoid It

Rebalance your portfolio at least once a year to maintain your desired risk level. Many 401(k) plans have an automatic rebalancing feature—turn it on if available.

9. Forgetting About Old 401(k) Accounts

If you’ve switched jobs multiple times, you might have old 401(k) accounts sitting with former employers.

Why It’s a Mistake

Having multiple accounts can be a hassle to track, and some plans charge high fees that erode your savings.

How to Avoid It

Consolidate your old 401(k)s into an IRA or your current employer’s plan. It’s easier to manage, and you’ll have more investment options to choose from.

10. Underestimating How Much You Need for Retirement

Many people assume they’ll need less money in retirement than they actually will.

Why It’s a Mistake

You may live longer than expected, and healthcare costs tend to skyrocket in retirement. If you don’t save enough, you risk outliving your money.

How to Avoid It

Use retirement calculators to estimate your future expenses and adjust your savings rate accordingly. A good rule of thumb is to aim for at least 15% of your salary (including employer contributions).

Final Thoughts

Avoiding these common 401(k) mistakes can make a huge difference in your retirement savings. The key is to be proactive—review your plan, understand your options, and adjust as needed. Your future self will thank you!