Anywhere but Rhode Island, this would be unbelievable. Rhode Island taxpayers who filed for the six month extension to pay their taxes may have to pay up to 25% of their owed amount in additional fees plus 18% interest on the overdue amount (in comparison to the 5% interest that the federal government charges):

The error stems from the original extension granted because of the severe spring flooding. Rhode Island taxpayers were permitted to pay their taxes and file their returns on May 11 instead of April 15. Those who sought a six-month extension were inadvertently given six months from May 11 instead of April 15.
[URI economist] Lardaro says it’s another case of the state not being business friendly. “It not only is an indication of that but also sends a signal that ‘We’re not business friendly and proud of it,'” Lardaro said.

This response is just too typical of the Rhode Island mindset:

But Ed Mazze, a professor of business administration at the University of Rhode Island, disagreed, saying the state should not be blamed for the situation. He says accountants and their clients should have known better. “If they’re not smart enough to call the state and ask if there is an extension, then shame on them,” Mazze told GoLocalProv.

Hey, maybe you’re not smart enough to live in our state. Why on Earth would you think that a six month extension would add six months to the date on which you actually were supposed to pay your taxes?
Of course, I’ll grant that we’ve allowed our government to operate as it does raises the question of whether we deserve what we get. But still: we’ve got people on the public payroll whose job it is to find recipients of public assistance funds. Welfare programs have been known to advertise. Would it have been too difficult, given the unique circumstances of a catastrophic flood during tax season, to send out a notice ensuring that those who filed for extensions understood the dates involved?