A source familiar with the meeting said that Trump flippantly made a comment along the lines of "'you might see my taxes one day'" or "'maybe I'll release them one day, who knows?'"
Sen. Bill Cassidy, a Louisiana Republican, was in the meeting and confirmed the remark.
"He just mentioned his tax returns. Everybody knows the controversies, everybody chuckled," Cassidy said, describing it as a nonchalant comment.
"So I wouldn't take it too seriously," he added.
Trump is the first president in modern times to not release his tax returns
. His financial dealings have come back into the spotlight since he's begun pushing for an overhaul to the tax code with a plan that he says would negatively affect wealthy people like him.
"I'm doing the right thing, and it's not good for me," he said about the tax plan last month in a speech in Indiana.
While Trump has reported hundreds of millions in income through financial disclosures, he has not made public his tax returns, which would show how much he pays in taxes and how the new plan would affect his tax bill
Another source briefed on the meeting confirmed Trump made the comment and said there was "nervous laughter" in the room.
The meeting was held with members of the Senate finance committee, the main panel in the Senate tasked with passing tax reform legislation. Republicans released a "framework" of the tax plan
last month that outlined the broad proposals of the plan but still lacked in detail.
In the meeting, the President reiterated some of the key components of the plan, such as increasing the child tax credit, reducing the corporate rate from 35% to 20%, and eliminating the estate tax.
"It's going to be a very big simplification," Trump said during a portion of the meeting that was open to the press. "So it's really tax cuts and reform, but I focus on tax cuts because it's such an important weapon to get our country really moving."
Senate Republicans, who hold a 52-48 majority, are set to pass a bill this week that will allow them to pass tax reform with only 50 votes rather than the usual 60 needed to overcome a filibuster.
Since Republicans can only afford to lose the support of two of their own, Trump has been actively trying to court Democrats. He met with Democratic members of the House ways and means committee last month and has been traveling to states that voted for him last year and have vulnerable Democratic senators up for re-election in 2018.
Among the Democrats invited to the White House on Wednesday were Sen. Ron Wyden of Oregon (the top Democrat on the Senate finance committee), Sen. Sherrod Brown of Ohio, Sen. Bob Casey of Pennsylvania, Sen. Claire McCaskill of Missouri, Sen. Bill Nelson of Florida and Sen. Debbie Stabenow of Michigan.
Brown's office said that he presented two bills to Trump that the senator believes would ignite a tone of a bipartisan spirit on tax reform. The first bill, the Working Families Tax Relief Act, increases the earned income tax credit and the child tax credit. The second bill, the Patriot Employers Tax Credit, would cut the corporate rate only for employers that keep jobs in the United States.
Democrats have largely objected to the Republican tax plan so far, arguing that -- contrary to what the President says -- it's too beneficial to the wealthy compared to the middle class.
Wyden said that he brought up in the meeting what he called a "grand canyon-sized gap" between the rhetoric and the reality of the Trump tax plan.
"One hand giveth, the other hand taketh away," he told CNN. "You double the standard deduction but you take away the personal and dependent exemptions."
Multiple Democratic senators said they brought up concerns about the tax plan disproportionately benefiting the wealthy.
Republicans, on the other hand, praised the meeting as productive.
"We all agreed tax reform should focus on helping middle-class families, and that's what our plan does," Sen. Rob Portman, R-Ohio, said in a statement.
Sen. John Cornyn, the Senate majority whip, said on the Senate floor Wednesday that the President expressed a desire for tax reform to be done on a bipartisan basis.
"What we are going to do is come up with what we think represents the closest thing to a consensus of those who are interested actually in pro-growth tax reform, what that would look like, and then open it up to Democrats and Republicans alike to offer their amendments to change it," he said.