If you’re like the rest of this planet, it isn’t until something actually gets set up in your life that you realize you did have a million and a half other questions to ask before doing it—but that’s okay, at least when it comes to 401k contribution limits. The nice thing about having your 401k set up is that you don’t have to worry about taking care of it. Your employer will deal with making sure that it runs the way it’s supposed to. (Unless you’re on an individual 401k plan, in which case . . . well, we’ll get to that in a paragraph or two.)

With that said, however, you will definitely want to know what’s going in and coming out of it and how much that amounts to. Even if you’re just starting out your employment and know that you have no hope of saving enough these first couple of years even to dream of surpassing your 401k contribution limits, you’ll want to know for later. Knowing your 401k contribution limits, whether before or after you set the account up, is important for three reasons. First, you want to avoid over-contributing. Second, you want to know if you’ll need an additional savings account. Third, you want to know all you can about catch-up contributions.

Over-contributing usually isn’t going to be as much of a financial problem as it is going to be a hassle. If you’ve been scrimping and saving all year only to realize you’ll have a few extra hundred or thousand dollars you can’t stick in your 401k, well, first, congratulations! Take a cruise. But if you want to hold onto that cash and make it work for you, it’s nice to have that second concern addressed (the additional savings account). If you know that your income exceeds your cost of living by a fair margin (as if you’re single and on a decently high salary), you want to have things prepared for putting away that money before, not after the check actually gets into your hands.

The last important reason to know about 401k contribution limits is to know about catch-up contributions. If you are early in your employment and your 401k doesn’t look to be taking away much of your paycheck, you can often make contributions beyond those usually permitted once you start having the money to do it, up to certain limits. It’s important to do the research yourself to know exactly what applies to your account and situation, but if you are on an employer’s 401(k) (current as of 2009), your 401k contribution limits are going to be $16,500 for your base contribution and $5,500 for your catch-up contributions (catch-up contributions apply if you are over 50).

Now, as we parenthetically mentioned, if you’re self-employed, the rules are a little bit different. For a solo 401k, your contribution limit is $49,000 (plus the $5,500 catch-up contribution if you’re over 50). So even if you are like the rest of this planet and only now realize you have all those questions about your 40(k)—well, knowing those limits ought to give you the right start.