"When we move up the ladder and people start having investments, and getting capital gains and money off of those investments, or maybe have self-employed income, you're looking at filing a Schedule C — as well as an A and a B," says Jim Barnash, a CFP financial advisor with SGL Financial. "It's not that you couldn't do that on your own, but you might miss opportunities where you leave money on the table and the IRS does not tap you on the shoulder and say, 'Oops, by the way, you missed that one.'"