There are so many things going on here. . .
1) Harry Reid might be telling the truth that someone told him that Romney can’t release his tax returns because they’ll show he paid zero taxes for the last 10 years. We could assume he’s telling the truth here, but the story that Romney didn’t pay any taxes in the last 10 years has to be false, because if true, the IRS would’ve caught up with him after about 3 years, and it would be public knowledge.
2) Romney has complex tax returns that also refer to his businesses and business partners, so there is plenty of stuff in there to pick at, I doubt any of it is illegal, or again the IRS would’ve caught him, but it could look bad politically.
3) Politifact is calling the story that Romney paid zero taxes false not the story that someone told Harry Reid this story.
4) Many tax experts have tried to figure out a way that Romney could’ve legally paid zero taxes in the last 10 years, and they can’t come up with a way, so he must’ve paid some taxes, probably 13% or 14% a year.
5) It’s a calculation that Romney is making that it’s better to hear President Obama call for him to release his tax returns, than to actually release them, and be forced to defend every deduction for a political standpoint.
6) to sum up Politifact made the right call it’s a false charge that Romney paid zero taxes for 10 years.