Here's virtually everything you need to know about a 401(k) plan:

  • It's one of the very best ways to save for your retirement. Few alternatives are better.
  • There's a good chance that your employer will give you money for participating in the company plan.
  • You should start contributing to your retirement plan as soon as possible.
  • If you are more than 10 years away from retirement, you'd probably fare best by putting all of the money that you defer into an equity index fund.

You may need to read no further than this. Seriously.

We wanted to get all the information we could to you right up front because this stuff is pretty important. Studies show that if you're the average Internet reader, your attention span is so limited that you've probably already clicked over to some other website by now, although the big bright words in red at the bottom of your screen just might have kept your attention. Ha! Got you to look!

Therefore, in an ongoing effort to keep your fingers from tapping out www.gotta-be-more-interesting-than-401(k), we'll try to keep things moving -- beginning with mentioning again that there could be free money involved. Hey, we're not going to be dispensing any free money around here, but your boss just may be. If you can get some of that, various other studies show that you'll be happy you stuck around here for a couple hundred words.

To begin at the beginning, in 1978, section 401(k) of the Internal Revenue Code authorized the use of a new type of deferred compensation retirement savings plan for the benefit of employees of most private firms. Employees who participate in employer-sponsored 401(k) plans choose to defer part of their salary, and the employees themselves determine how much of their salary to defer and how to invest the money.

Participating employees choose to take home a smaller paycheck because there are several major advantages to saving for retirement through a 401(k), including:

  • Immediate tax savings on contributions
  • Tax-deferral of any investment earnings
  • In-service loans and withdrawals
  • Free money

Those first two or three might not have looked quite so interesting, but the free money item is an eye-catcher, ain't it? Before we get to that (we're saving the best for last) let's go over the first three, because they aren't so bad either.

When you defer compensation into an employer-sponsored 401(k) program, you immediately start paying less to Uncle Sam. The amount that you decide to defer is money that comes out of your paycheck before income taxes come out of it, and the money goes right into an account with your name on it. That's money that you're keeping out of the hands of the federal and state governments until you retire. (And, hey, you may decide to retire in some state where there are no income taxes.)

Just as important, because the taxes on the investment earnings are also deferred, you're not paying any taxes on anything that your deferred compensation earns until years from now when you're retired.

Another feature of some 401(k) plans is that Fools can lend back to ourselves some of the money that has been deferred for something important like buying a house or meeting expenses should an emergency arise. This is money that we can borrow from ourselves, rather than from a bank.

Fools, though, will borrow from a 401(k) plan only as a last resort. That's because we may change jobs before the loan is repaid. If we do, that loan is immediately payable with interest. Fail to come up with the necessary cash for that repayment, and there's a stiff price to be paid. Uncle Sammy will call the unpaid debt a "deemed distribution" from the 401(k). It will be taxed and -- assuming we're younger than age 59 1/2 -- penalized 10% as well for an early withdrawal of the money.

Additionally, the interest we pay ourselves on the loan comes from money on which we've already paid taxes. But for 401(k) purposes, it will count as untaxed earnings. That means we will pay taxes on that money again in retirement when we make withdrawals from the 401(k). Bummer on both counts! Thus, while the loan feature is attractive to some, Fools think it's really something to use only when all else fails.

The best reason of all to contribute to a 401(k) or other deferred compensation plan is that many employers match a portion of the money deferred by their employees. That's right -- these employers are giving away money. Woo-hoo! Find out about whether your employer is providing matching contributions. If it is, you absolutely should commit yourself to deferring every dollar you can up to the amount that your employer is willing to match.

How big a difference can employer matching make? Well, if your employer is matching your contributions dollar for dollar, you'll be, of course, doubling the amount of money put away for your retirement.

And that's the ultimate reason for contributing to your 401(k): more money for retirement. Social Security pays, on average, less than $11,000 a year. And fewer and fewer employers offer traditional pension plans. So if you want to retire, you'll need to rely mostly on personal savings. Using your 401(k) is one of the best ways build that nest egg.

For more on 401(k)s and other ways to save for your golden years, visit our Retirement area. And if you'd like to talk to an expert about your particular situation, check out TMF Money Advisor.