What is Romney hiding?

Mitt Romney is taking great pains to avoid disclosing exactly where his money is invested, making use of what the Washington Post calls "an obscure exception in federal ethics laws" to avoid public scrutiny.

The Post reports that in 48 of his Bain Capital accounts, "Romney declined on his financial disclosure forms to identify the underlying assets, including his holdings in a company that moved U.S. jobs to China and a California firm once owned by Bain that filed for bankruptcy years ago and laid off more than 1,000 workers." We only know these limited examples because these companies were required to disclose information publicly. But the majority of underlying assets—specific investments—remain hidden because Romney is protected by a confidentiality agreement with his former firm.

Here's what that means in layman's terms, courtesy of OFA campaign manager Jim Messina: "Romney has put his personal financial assets in a black box and hid the key, attempting to play by a different set of rules than any candidate in recent history."

The Post also notes that "several outside experts across the political spectrum" agree that "Romney's disclosure is the most opaque they have encountered."

That's why we've been demanding for months that Romney release his tax returns. Until he does, we won't fully know how much of his money is in offshore accounts, controversial companies, or whether his financial decisions show any other major conflicts of interests.

The little we do know is troubling: Romney pays a shockingly low 13.9 percent tax rate—a rate that is lower than most middle-class families and even most millionaires. Romney has large investments in notorious overseas tax havens like the Cayman Islands and Bermuda. He had $3 million stashed away in a Swiss bank account that was closed in recent years for fear of political embarrassment. Some of this information was omitted from the personal financial disclosure Romney filed last year—a requirement for all those seeking federal office. It was revealed months later when Romney agreed to release one year of tax returns after mounting public pressure.

What else could Romney possibly be hiding? We won't know without at least a decade's worth of tax returns.

So as Romney continues to prove his willingness to hide critical information and play by his own set of rules, we need to turn up the pressure once again and demand basic transparency and accountability from a man who aspires to the highest office. Decades of presidential candidates, including President Obama, have done so ever since Mitt's own father, George Romney, set the standard in 1968 by releasing 12 years' worth.

We know he has them. Just four years ago, when Romney was being vetted as a potential 2008 running mate, he gladly forked over 23 years' worth of returns. The American people deserve the same.

Tweet @MittRomney and use the hashtag #WhatsRomneyHiding to demand he release more tax returns.