Just to follow up on this tax return issue that is playing havoc with Mitt Romney’s Presidential campaign, it turns out that the returns he claimed to have fully disclosed were not fully disclosed:

Mitt Romney has not released his full tax records from 2010, including key documentation connected to his Swiss bank account [...]

Romney released his 2010 tax return in January of this year, a document that first informed voters about the existence of his Swiss bank account and financial activities in Bermuda and the Cayman Islands. But people who own foreign bank accounts are required to file a separate document with the IRS that provides additional details on such overseas bank holdings, and Romney has not released that form to the public.

The Romney campaign did not respond to HuffPost’s request to view the document.

Tax experts say it is almost certain that Romney did file the form, known as a Report on Foreign Bank and Financial Accounts, or “FBAR” in accountant slang. The penalty for not filing an FBAR can be severe, and the IRS would have expected to receive the form since Romney listed the Swiss bank account on his tax return. Listing the account on his tax return and then failing to file the subsequent FBAR would have been asking for a hefty fine, and would probably have heightened IRS scrutiny of prior tax filings.

This ought to lead to more speculation about that Swiss bank account, and whether Romney took the tax amnesty on that (a de facto admission of illegal tax dodging) in 2009. I don’t know for sure if such a designation would show up on a 2010 FBAR form, but it certainly would be a feature of the 2009 form if he took the amnesty in that year. And that is conveniently the cutoff for what Romney will release. We know that Romney disclosed the Swiss account in 2010; we do not have that information for 2009, the year of the amnesty. Romney’s account was with the same bank, UBS, targeted by the IRS for tax haven abuse. A lot of things line up here.

“It’s unclear why he would have valued the Swiss bank account secrecy, and it wouldn’t have enabled him legally to avoid U.S. tax,” said Daniel Shaviro, a tax professor at New York University School of Law. “This is why there’s speculation that he was into the amnesty program.”

But Shaviro and other tax experts note that one of the principal benefits of the amnesty program is its anonymity. Nobody who received amnesty from the IRS would ever have to tell the public they’d held a Swiss bank account. Any politician who had received amnesty could have simply shut down their account and washed his or her hands of any political liability. And once the IRS was aware of the account, maintaining it would have had no tax benefits.

The 2010 tax return shows no tax benefit from the account. An absence of the account on previous returns would be essentially an admission of tax dodging, as Romney’s team has already acknowledged he had the Swiss account since 2003.

Meanwhile, Democrats have introduced a bill that they might as well call the “Mitt Romney’s Tax Situation Bill of 2012.”

On Wednesday, Senate Majority Whip Dick Durbin (D-IL) and Sen. Carl Levin (D-MI) took to the floor to talk up the Financial Disclosure to Reduce Tax Haven Abuse Act, which was introduced in March. It would force candidates and their spouses to file a disclosure form listing the identity, value and location of finances held in jurisdiction deemed a tax haven by the U.S. treasury, such as the Cayman Islands and Switzerland. Current law does not require such disclosure.

The senators called it part of a long battle to crack down on the abuse of tax havens, but after their speeches, Durbin admitted to reporters that the timing of his renewed push isn’t a coincidence.

“My research suggests Mitt Romney is the first presidential candidate in American history with a Swiss bank account,” the No. 2 Democrat told reporters. “And obviously this has been a topic, as well as his use of these tax havens and shelters. He has also failed to disclose income tax returns to the same level of previous presidential candidates over the last 36 years. And it raises questions.”

Carl Levin has been on this tax haven issue for quite a while, but it does dovetail with the current debate, not just because of the election, but because of Levin’s SPSCI work on HSBC, the bank which laundered money from tax havens like the Cayman Islands to open up the US financial system for drug lords and terrorist financiers.