Um...except for the tax returns, you mean? Because I'm pretty sure you're hiding those:
"We have been very transparent to what's legally required of us,” [Ann Romney] said. “There's going to be no more tax releases given."
Mrs. Romney said if they release any more information, "it will only give them more ammunition."
In regards to their finances, she said "there's nothing we're hiding."
I love this "only give them more ammunition" argument. It's basically a transparent admission of guilt, which means it's the most transparent part of the Romney campaign.