US Democratic presidential contender Bernie Sanders has released 10 years of tax returns, providing details of his growing status as a millionaire fuelled by a sharp jump in income from book royalties since his losing 2016 White House run.
Sanders, a US senator who routinely rails against the "millionaires and billionaires" he says have rigged the system to protect their wealth and power, had an adjusted gross income of $US561,293 in 2018, down from $US1,131,925 in 2017, the returns showed.
Sanders augmented his Senate salary with book royalties, particularly in 2016 and 2017 when he made more than $US800,000 each year in royalties.
Sanders has published three books since the start of his first White House run, including bestsellers Our Revolution and Where We Go From Here.
Sanders had faced mounting pressure to release his taxes, with critics saying the democratic socialist's millionaire status undercut his populist economic message.
He made no apologies for his financial well-being, telling the New York Times recently that "if you write a best-selling book, you can be a millionaire, too."
On Monday, Sanders took a more measured tone in releasing his returns, making reference to his upbringing in a Brooklyn family of limited financial resources.
"These tax returns show that our family has been fortunate. I am very grateful for that, as I grew up in a family that lived paycheck to paycheck and I know the stress of economic insecurity," Sanders said in a statement accompanying the returns.
The interest in presidential contenders and their taxes has jumped since Republican President Donald Trump shattered decades of tradition during the 2016 campaign by refusing to release his returns - a stance he has continued since entering the White House.
Several in the growing field of Democratic 2020 contenders, including Senators Kirsten Gillibrand, Amy Klobuchar, Kamala Harris and Elizabeth Warren, and Governor Jay Inslee of Washington, have released their 2018 returns in recent weeks.
Most other Democratic contenders have pledged to do the same soon.
Sanders faced criticism for only releasing his 2014 returns during his 2016 Democratic primary battle with Hillary Clinton, a millionaire whom he often derided for giving paid speeches to Wall Street.
As part of his policy agenda, Sanders has proposed a big expansion of the estate tax.
Australian Associated Press