If economists ran the tax system, there would be virtually no exemptions or loopholes. But economists don’t run the tax system! Instead, businesses, rich people, Congressmen and attorneys spend a shockingly large amount of time lobbying for tax breaks or exploiting the ones that exist. When the modern income tax was created in 1913, the code was 27 pages long. Last year, it was 5,296 pages. What in the world does it say? After surveying 20 accountants, tax lawyers and policy wonks, we’ve boiled down their arcane knowledge to this short list of things you might want to know.

So what’s the easiest way to cheat on your taxes?

Run your own company. More specifically, as Greg Kyte, a Utah C.P.A., puts it, be the sole proprietor of a Schedule C business. Then you can buy stuff for yourself and probably write it off as a business expense. “You can look through your receipts for the year and say, ‘Here’s some stuff I bought at Home Depot,’ ” says Kyte (who, for the record, says he never does this). “The I.R.S. would have no idea if I bought that for my house or for my business.” There were more than 20 million Schedule C returns filed in 2009, with receipts of more than $1.2 trillion.

Upstanding Schedule C filers have options, too. They can legally write off payment for office work done by family members, even if they’re in middle school. “I’ve seen people with infant children claiming that their kids are doing work,” says Howard Rosen, a St. Louis-based C.P.A. “I’m talking about a 3-year-old doing filing,” Rosen says. “He didn’t even know the alphabet.”

How often do people cheat?

For 2006, the most recent year for which data are available, the I.R.S. collected 86 percent of what it was owed in taxes. Most of this $385 billion shortfall came from underreporting income, which is often more creative than it sounds. Gambling winnings, for example, are taxable, but losses are deductible — and some people greatly exaggerate their losses. “It’s not unheard-of for gamblers to go to the track and pick up tickets for losing bets that would be thrown on the floor,” says Mark Blood, a C.P.A. in Rochester. “I had an examination once where a number of tickets the client had given me to support losses had footprints on them.” The agent disallowed the deductions.