"I did what was an nearly an impossible thing to do for a Republican - easily won the Electoral College!" Trump is the first major party nominee in more than 40 years to not release his tax returns, saying it was because he was under audit.
Rallies were held in more than a dozen cities nationwide Saturday, just days before the deadline for taxpayers to file their returns on Tuesday.
Seventy-one-year-old Ilene Singh said he's wrong.
In criticizing the protests, Mr. Trump questioned the motives of the demonstrators and said the question of his tax returns was settled in the November election.
"We are taking the gloves off to say knock off the secrecy Mr President", said Senator Ron Wyden of OR, the ranking Democrat on the Senate Finance Committee.
Though nearly all news media discussed North Korea's failed missile launch, Trump was instead complaining about the Tax Day marches.
The demonstrations were timed to coincide with the traditional April 15 deadline for annual tax filings, a massive date on the calendar for USA households, and resulted in dozens of arrests.
Moments after he defended no longer calling China a currency manipulator, now that they are giving him a helping hand with North Korea, Trump dismissed calls for his tax returns by responding on Twitter. "I hope Republicans see it".
Most of the demonstrations proved peaceful, but in Berkeley, Calif., police arrested 13 people and confiscated knives and makeshift weapons after fistfights broke out between Trump opponents and supporters.
Other events took place without major incidents in such US cities as Chicago, New York, Seattle and Washington, D.C., and outside pf Trump's south Florida resort home, Mar-a-Lago.
"His reputation.as a businessman and, more importantly, as a true American, a person who is concerned with American values, would be totally destroyed if all his financial information was made public", said Mike Mannshardt, a retired teacher.
Nancy Traver, of Silver Spring, Maryland, who was at the Washington march said: "Every president, Democratic and Republican for years has showed, has revealed his tax returns, so why shouldn't Trump?"
For four decades, presidents and major-party nominees have released some of their tax returns, with the exception of Gerald Ford. Protesters say Americans deserve to know about Trump's potential conflicts of interest.
Back in January, the Trump administration tried to quietly put the issue under the rug when White House advisor Kellyanne Connway told ABC News Trump would not release his tax returns because voters "didn't care."
Last month, MSNBC reported on two pages of Trump's 2005 tax return that were obtained by investigative reporter David Cay Johnston and showed that he paid $38 million in taxes on over $150 million in income.
"We do care. We want to see his taxes", said Ann Demerlis, who was among hundreds who marched in Philadelphia from City Hall to an area in front of historic Independence Hall, carrying signs and chanting, "We want your taxes now!"