Hillary Clinton has released her 2015 tax returns, which show the Democratic presidential nominee and her husband had US$10.75 million ($14.94m) in income that year and paid an effective federal tax rate of 34.2 per cent.
In 2015 the Clintons made US$1m in charitable contributions, mostly to the Clinton Foundation; former president Bill Clinton brought in nearly US$5.3m in speaking fees; and the former secretary of state reported income of US$3m for her book on her tenure at the State Department.
Clinton's running mate, US Senator Tim Kaine of Virginia, along with his wife, Anne Holton, released 10 years of tax returns. They paid an effective federal tax rate of 20.3 per cent in 2015.
"Hillary Clinton and Tim Kaine continue to set the standard for financial transparency," Clinton campaign aide Jennifer Palmieri said. "In stark contrast, Donald Trump is hiding behind fake excuses and backtracking on his previous promises to release his tax returns."
It is customary for US presidential candidates to make their tax returns public, although they are not required by law to do so.
Trump and his lawyers have cited an audit by the Internal Revenue Service as a reason for his refusal to release his returns. Trump also has said his taxes are no one's business and that they reveal little.
"Your move," Clinton campaign aide Ian Sams said on Twitter, linking to the Democratic nominee's returns.
The Trump campaign dismissed Clinton's action, saying: "This document release is nothing more than an attempt at distraction and misdirection" from controversy about her use of a private email server when she was secretary of state.
The IRS has said Trump can release his tax returns while under audit.
On Thursday Trump's special counsel, Michael Cohen, told CNN he would not allow Trump to release them until the audits were complete.
Trump's critics, including 2012 Republican presidential candidate Mitt Romney and other fellow Republicans, have said his refusal raises questions about his net worth, his charitable contributions, his business dealings and other ties, including with Russia.
Clinton has pounced on the issue, releasing an online video highlighting high-profile Republicans urging Trump to release his taxes. On Friday she raised the issue during an economic speech in Michigan.
Politico has reported Trump paid zero to very little in tax for two years in the 1990s, and a New York Times business columnist on Friday quoted several tax lawyers and accountants saying that could still be the case.
Federal tax rates have become an issue in the presidential election.
Clinton has endorsed a rule named after billionaire Warren Buffett that would ensure those making more than US$1m a year pay tax of at least 30 per cent. President Barack Obama also backs the proposal.