"Here's a pretty incredible fact: There is a non-zero chance that Donald Trump isn't paying (asterisk) any (asterisk) taxes", Clinton tweeted, after releasing her own returns.
Clinton then made an Olympics reference to slam her Republican opponent on trade. Clinton attempted to draw contrasts when she spoke at a rally Wednesday in Des Moines, Iowa.
Hillary Clinton swung hard at Donald Trump in an economic-policy speech in MI on Thursday, saying the Republican nominee's trade policies are based on "fear". Faced with Trump's pessimism about the state of the country, she often tries to talk up the state of the economy under a president whose administration she served in for four years.
Mr Trump said this week he wants to cut taxes for businesses and workers, and go with a three-bracket income tax system that is close to what House Republicans have recommended.
Many voters have signaled their desire for dramatic change - from the success of Bernie Sanders insurgent challenge to Clinton to Trump's successful bid for the GOP nomination against a host of establishment favorites - in a nation facing stagnant wages, intense anxiety and rising income inequality. Trump has said he won't release them until an IRS audit is complete, breaking traditional with every presidential candidate in recent history.
Hillary and Bill Clinton earned $10.6 million a year ago, according to a tax filing released by her campaign Friday that sought to pressure presidential rival Donald Trump to disclose his tax returns.
During her speech in Warren, Clinton touched on investing $275 million into infrastructure, raising the minimum wage, helping cities like Detroit and Flint, and appointing the first chief trade prosecutor. Her campaign also released returns from running mate Tim Kaine and his wife.
"I don't understand why Trump's against that", Clinton said of Trump's opposition to guaranteeing equal pay for women. "The answer is not to rant and rave - or to cut us off from the world".
With few exceptions, Mr Trump has provided more of a philosophical basis for an economic plan than specifics, although he did call for greater child care deductions for families.
"Which candidate will stand up for working families and the middle class and actually deliver results, and which one has a plan that only benefits millionaires like himself?" a Clinton campaign official who had seen her planned remarks told the Times was the basic idea behind the speech.
Both candidates used MI to disclose their economic proposals, while taking a shot or two at each other along the way.
"And I will say this, and I say this to you very strongly, if short-circuit Hillary Clinton ever gets elected, it's only going to be worse".
That claim, rated "mostly false" by Politifact, didn't take into account the two large real estate assets - the Clintons' houses in NY and Washington, D.C. - and the couple's earning potential from Bill Clinton being a former president, the website noted.
CNN reports today that Trump's comments did prompt a conversation between the Secret Service charged with protecting presidential candidates and the Trump campaign. Trump insisted he was never advocating violence against Clinton.
Just hours before her address, Trump unleashed another round of attacks on Democrats, calling Obama the "founder" of the Islamic State militant group - and Clinton, its co-founder.
Clinton is leading Trump in recent polls of MI voters. Lerer reported from Washington.