Mitt Romney is running for president, so it's important we know everything about him.

In particular, I think it's time we learned what's in his tax returns. To date he has released only one year of returns for 2010. What on earth is he trying to hide?

We already know Romney has invested untold millions in multiple tax heavens around the world, a ploy that allows the super-rich to evade US tax laws, but the staggering sums that are piling up - he has $30 million dollars in the Caymen Islands alone - are a bizarre and insulting precedent for a United States presidential candidate.

We also know that Romney appears to believe that taxes are for the little people. We know this because in 2010 and 2011 he paid $6.2 million in federal tax on $42.5 million in income. That means he paid a tax rate of about $15 percent, which is a rate that most middle class tax payers can only dream of.

So if there's nothing to hide, and we assume there isn't, why is he hiding it? Has he made use of off shore havens to defer or avoid paying his federal income taxes? Did he buy any illegal or gray area tax shelters? Has an IRS audit ever uncovered any serious problems with any of his tax returns? Has it all been on the up and up, has it all been legal?

These are pretty simple questions and they deserve an answer from anyone who puts themselves forward to be commander in chief.

We already know that at Bain Romney made use of the 'covered interest' tax loophole that allowed him to treat his fees there as if they were capital gains (15% tax) rather than wages (35% tax). That's perfectly legal, if not exactly perfectly patriotic. But how many people are evening reporting on that yet?

The silence from the Romney camp is unsettling.