Democratic presidential nominee Hillary Clinton has released her 2015 federal income tax return, adding to the pressure on rival Donald Trump to do the same.

Hillary Clinton paid an effective federal tax rate of 34.2% in 2015.

Running mate Tim Kaine, along with his wife Anne Holton, paid a rate of 20.3%, his returns show.

Billionaire Donald Trump has refused to release his.

Presidential candidates typically release their tax returns to the media to show their effective tax rate, charitable donations and other financial details.

Donald Trump, who has released a self-reported financial disclosure form, said he will not make his income tax return public until the Internal Revenue Service (IRS) completes audits of them.

Hillary and Bill Clinton were to headline Senator Tom Harkin’s annual steak fry fundraiser in rural Indianola

The IRS has said Donald Trump is free to release his returns. Donald Trump would be the first presidential candidate in decades not to release his returns.

Richard Nixon released his federal income tax return in 1973, starting an informal precedent.

In 2012, then-Republican presidential candidate Mitt Romney reluctantly released his returns.

The returns became a campaign issue after the documents showed Mitt Romeny paid an effective tax rate of 14.1%, much lower than the typical rate for top earners.

“Hillary Clinton and Tim Kaine continue to set the standard for financial transparency,” said a Clinton campaign spokeswoman, who called on Donald Trump to do the same.

Hillary and Bill Clinton made most of their money in 2015 from business income, namely consulting, speaking and book royalties, for a total of $10.1 million between the couple.

Bill Clinton spent $500,000 in travel as part of the speaking portion of his business, while the former secretary of state had about $250,000 in travel expenses for her speaking business.

Half of their deductions are charitable giving – including a $1 million donation to the Clinton Foundation

Hillary Clinton’s return was filed jointly with her husband former President Bill Clinton. The couple earned more than $10 million in 2015, the documents say.

Most of the income came from Bill Clinton’s speaking fees as Hillary Clinton has been campaigning for president.

Hillary Clinton earned about $3 million from book royalties.

Bill and Hillary Clinton have disclosed tax returns for every year since 1977.