Matthew Weinstein, of Progressive Maryland, talks to post office customers about tax loopholes.

While a chunk of the earnings of most law-abiding citizens is now winging its way toward an IRS service center, the profits of most major U.S. corporations are living it up in some tropical paradise.

The big companies’ dough is chillin’ in the Cayman Islands, or one of the other offshore tax havens where companies like AIG and Morgan Stanley hide their profits.

So said Johanna Neumann, yesterday, state director of the Maryland Public Interest Reseacrh Group, as she and other taxpayer advocates rallied outside Baltimore’s main Post Office to urge support for President Obama’s tax reform proposals.

“These corporations are avoiding paying as much as $100 billion every year in taxes,” Neumann said, adding that Maryland corporations avoid about $1.9 billion a year, according to the group’s recently-released report.

That number puts a little perspective on the amount that Maryland Comptroller Peter Franchot pointed out is owed to Maryland by 50 businesses and individuals, tax scofflaws who owe Maryland nearly $6 million in taxes.