I guess you could release 10 years worth of tax returns…

“Senate Majority Leader Harry Reid (D-NV) told the Huffington Post that a Bain Capital investor told him that Mitt Romney didn’t pay any taxes for at least a decade. The person also told Reid that Romney’s wealth was significantly more than the $250 million estimated. “Tellingly, neither Reid nor his office would reveal who the investor was, making it impossible to verify if the accusation is true. And as his quote makes clear, he’s uncertain if the information is accurate… But there is limited political downside to the type of open speculation that Reid is making, so long as Romney refuses to budge on the issue of his tax returns. Increasingly, other Democrats are growing more assertive in their goading.”"