Though not everyone gets access to a 401(k), a good 79% of U.S. employees work for companies that sponsor these plans. And those who choose to participate in their employers' 401(k)s stand to reap a number of benefits. Not only are 401(k) contributions tax-free, but the associated annual limits are much higher than those of an IRA. For the current tax year, workers under 50 can put up to $18,000 away, while those 50 and older can max out at $24,000.

If you're already participating in your company's 401(k), you're off to a good start retirement-wise. That said, a 401(k) isn't something you can set and forget. If it's been some time since you've put much real thought into your 401(k), here are a few questions you should be asking yourself.

"401k" in gold block letters on a wooden background

Image source: Getty Images.

1. How are my investments doing?

Contributing money to a 401(k) is only part of the picture; it's also on you to make sure your investments are generating a reasonably decent return. Historically, the stock market has delivered a 9% return more or less, so your goal should be to put your money into funds that offer a similar or better return without exposing you to too much additional risk.

That said, your funds' performance can fluctuate over time, and while you don't necessarily need to move your money the moment one of your investments takes a dip, you should be vigilant about monitoring your returns on a quarterly basis. If you notice a downward trend, or see that your returns seem to be capping out at a certain level, it pays to explore alternate options that might do more for your money.

Keep in mind that even a 1% or 2% variation in annual returns could have a huge impact on your account value over time. The following table illustrates how your nest egg will fare based on your investments' performance:

Average Yearly Return on Investment

Total Accumulated Over 30 Years

(Assumes $300 Monthly Contribution)

3%

$171,000

5%

$239,000

7%

$340,000

9%

$491,000

Table and calculations by author.

As you can see, earning 7% on your investments versus 9% could reduce your nest egg by over $150,000 over a 30-year period when you're contributing $300 a month. That's why you'll need to keep tabs on your investments and switch them up as necessary.

2. Am I contributing enough to get my full employer match?

An estimated 92% of companies that offer a 401(k) also match employee contributions to varying degrees. Yet a good 25% of workers don't put in enough of their own money to take full advantage.

The typical employee who fails to capitalize on a full employer match ends up forgoing $1,336 each year, and lower earners -- those making less than $40,000 annually -- are the most likely to miss out. The problem, however, is that when you pass up free money in the form of a 401(k) match, you're not just losing out on that base amount, but also on whatever growth it could've achieved. In fact, if you were to add $1,336 to your 401(k) each year, you'd have an extra $126,000 in three decades' time if your investments were to generate an average annual 7% return. And that's not the sort of sum you want to relinquish.

That's why it always pays to contribute enough money to snag your full employer match. Keep in mind, however, that the criteria for doing so can change over time, so stay current on your plan's rules.

3. Am I saving as much as I could be?

Though you're allowed to put up to $18,000 or $24,000 a year into a 401(k), depending on your age, most workers aren't able to hit that limit. But even if you can't max out your contributions, the more you increase them, the better you'll fare in retirement.

If you've recently gotten a raise, for example, it pays to filter whatever extra money comes into your paychecks directly into your 401(k). Since it's not cash you've come to rely on for paying the bills, allocating it to your retirement account will be totally painless if you do so from the start. The same applies if you receive a bonus at work, or come into any sort of unexpected money. Finally, if your living expenses have recently gone down (say, you moved in with your partner and are sharing the rent), consider taking that extra money and sticking it in your 401(k) -- before you find a different use for it.

The more thought you put into your 401(k), the better it'll serve you in retirement. Be proactive in monitoring your account performance and savings rate, and you'll be more likely to make the most of this key savings opportunity.

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