It turns out that Donald Trump, he of the non-released tax filings, claimed a 1995 income loss so large - $916 million - that the tax software back then couldn't handle it; it didn't have enough space for all the numbers. His lawyer had to separately type in -91 on front of 5,729,293 to report the loss.
Such losses can be claimed against taxes owed for three prior years and 15 future years, leading the New York Times, which broke the story, to conclude that "it could have allowed him to legally avoid paying any federal income taxes for up to 18 years."
To the extent that the story made a splash, it's certainly not because it disabused anyone of the notion that Trump has been sending big checks to the IRS. The conventional wisdom, as purveyed by Hillary Clinton in their first debate, is that he pays little to no taxes, which is why he won't release the returns to the public. The leaked returns just confirm our priors.
Trump even went as far as to claim, in response to Clinton's allegations, that not paying taxes just means he's "smart."