It seems strange this has not been brought up by the news media;perhaps they are not liberal but just branded by the right to slide under closer scrutiny.
Anyway this gives a little more information on "mitt" and also should make you aware he has good lawyers! probably the best money can buy! It certainly makes me aware of his real character!
Here's What Happened The Last Time Mitt Romney Refused To Release His Tax Returns: http://www.businessinsider.com/mitt-romney-tax-returns-release-massachusetts-governor-election-obama-2012-7