What about load funds? My girlfriend was being sold Class A shares with a 5% upfront charge. I told her to buy the Class C. Should I have picked the B? Kevin Walsh

Weeding your way through a mutual fund's expenses and sales charges can make doing your taxes seem like a real treat.

When you buy a load fund, you have to decide between several different payment options -- all of which have hooks and catches that aren't easy to see or understand.

Knowing how these sales charges work is crucial. Several big-name, no-load fund companies, like Invesco, are slapping sales charges on their existing funds or adding load funds to their lineups. And if you got burned during the bull market and now want some advice, you might wind up turning to a financial adviser or broker who would love to sell you some load funds.

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But you shouldn't blindly trust your broker or financial adviser to tell you which choice is best for you. Instead, you should go in armed and ready to ask some hard questions.

ABC: Always Be Charging

Most load funds come in three basic share classes: A, B or C. These share classes give you different ways of paying the sales charges that are used to compensate the financial professional who's selling you the fund. You're paying for that person's advice.

It sounds simple, but look closer and your head might start to spin.

The A shares come with a front-end load that will typically run from 5.25% to 5.75%. You pay this entire charge upfront. But this fund's annual operating expenses, which all mutual funds have, will probably be lower than the annual expenses on the B and C shares. So you'll pay a fat fee initially, but you should get lower expenses in the long run. And you won't get hit with a sales charge when you sell.

Generally, the A shares are better for investors who are going to hold a fund for more than five years. You don't want to pay this upfront charge and then sell the fund in a year or two. You'll want to wait long enough to recoup that initial fee and then some.

The A shares are also designed for investors who are investing a big chunk of money all at once. That's because the load is generally tiered, according to the amount of money you invest. At Oppenheimer Funds, for example, the 5.75% upfront sales charge falls to 5.5% if you invest between $25,000 and $50,000. The more you invest, the lower it goes.

If you're investing a large amount of money, a fund company probably won't even let you buy another class of shares. Why should you pay a load when you don't have to? "If you try to put $1 million in B shares, a fund company will usually refuse and say it has to go in A," says Morningstar's Peter Di Teresa.

B for Back-End

The B shares get a lot more complicated. Rather than paying a load when you buy, you'll pay a charge when you sell the B shares of a fund. This back-end load has a nifty name: a contingent deferred sales charge, lovingly referred to as the CDSC in the fund business. The longer you own the fund, the lower this charge will go.

On Oppenheimer's B share funds, you'll pay 5% if you sell within the first year of ownership. That load falls to 4% after one year, 3% after two years, and down from there. For money that's been in the fund for six years or more, the back-end sales charge goes away, and those B shares convert to A shares, which usually carry a lower expense ratio.

Both the A and B shares are made for investors who are going to hold a fund for several -- if not many -- years. At first glance, the B shares might look like the worse of the two options. But that's not necessarily true. "Most B shares ultimately convert to A shares and it can turn out to be a wash," says Di Teresa.

Few Reasons for C

The C shares, on the other hand, tend to be a universally bad deal. You don't have upfront or back-end charges to worry about. Instead, these shares come with a so-called level load. (Although you might get hit with a 1% charge if you sell in the first year.) Translation: You'll pay consistently higher annual expenses every year.

The fund's 12b-1 fee, which is used to compensate the broker, is higher and boosts the fund's annual expenses noticeably. For example, Oppenheimer Discovery's A shares charge 1.25% each year in expenses, according to Morningstar. The C shares, however, charge 2.01%.

You only need to look at the C shares if you're planning to hold a fund for just a year or two.

That explains how these share classes work, but you'll still have to figure out which one to use and when. One place that can help is the the share-cost calculator on the

Securities and Exchange Commission's

Web site. You should be prepared to plug in plenty of pertinent information, such as how long you plan to own the fund and the investment amount.

You should also look in a fund's prospectus. Yes, that dreadfully dull document. Every prospectus must contain a table of fees that shows you how much you'd pay in fees based on a hypothetical investment. These examples probably won't fit your exact situation, but they are expressed in actual dollar amounts. As a result, you can quickly see which share class will probably cost you the most money based on how long you plan to own the fund.

These tables will be a vivid reminder that every dollar that you pay in fees and sales charges is a dollar that doesn't wind up in your wallet.