Perhaps you’re an investor in mutual funds or you’re interested in putting some money into them. You’re not alone. The Investment Company Institute estimates that 56.2 million households owned mutual funds in mid-2017. But despite their popularity, the tax rules involved in selling mutual fund shares can be complex. Tax basics If you sell appreciated mutual fund shares that you’ve owned for more than one year, the resulting profit will be a long-term capital gain. As such, the maximum federal income tax rate will be 20%, and you may also owe the 3.8% net investment income tax. When a mutual fund investor sells shares, gain or loss is measured by the difference between the amount realized from the sale and the investor’s basis in the shares. One difficulty is that certain mutual fund transactions are treated as sales even though they might not be thought of as such. Another problem may arise in determining your basis for shares sold. What’s considered a sale It’s obvious that a sale oc...