From Rick Newman at Yahoo Finance:
Donald Trump may pay little in taxes, but nobody's accusing him of breaking the law or cheating—and that may be the biggest revelation to come from the recent leak of Trump tax documents.As for Trump and his taxes, remember, liberal Democrat Sen. Harry Reid (D-NV), then the majority leader in the upper chamber, falsely claimed that the 2012 Republican nominee, Mitt Romney, paid no income tax for ten years.
The New York Times obtained a few pages from Trump’s 1995 returns showing the Republican presidential nominee paid no tax that year, and also claimed a $916 million loss that would have reduced taxes in future years. If Trump's federal tax rate is 0 or even in the single digits, he will have the lightest tax liability of any presidential candidate of the last 25 years, and possibly in the 103 years the United States has had an income tax.
Trump’s tax strategy is completely justifiable, however, given tax rules for losses. Real-estate developers enjoy some of the most generous tax breaks on the books, and Trump undoubtedly exploits the same forgiving laws that every other developer does.
"The law is very, very favorable to commercial real estate," says Lee Sheppard, contributing editor at Tax Analysts. "The tax law buys back your business losses by allowing carryovers to future years."