Richard Neal, the Democratic chairman of the House Ways and Means Committee, submitted his long-awaited request for President Trump’s tax returns on Wednesday.

The Massachusetts representative requested six years' worth of Trump’s personal and business tax returns, setting up a potential major legal conflict with the administration. Democrats believe the tax information would give them insight into any potential ethical or legal conflicts of interest Trump may have.

“Congress, as a co-equal branch of government, has a duty to conduct oversight of departments and officials,” Neal wrote in the letter to IRS Commissioner Charles Rettig. “The Ways and Means Committee in particular has a responsibility to conduct oversight of our voluntary Federal tax system and determine how Americans – including those elected to our highest office – are complying with those laws."

Neal requested Trump’s tax information by April 10. Rettig is scheduled to testify before House and Senate committees on April 9 and 10.

By law, the chairs of the congressional tax policy committees can request tax information for different businesses and individuals, without having to have their permission. Unauthorized release of that information, however, is a felony. If the committee does obtain them and Democrats believe they will be in the public interest, the committee could vote to release them to the broader House of Representatives, which could in turn vote to make them public. The legality of that may be a part of the administration’s challenge, if one comes.

Trump reacted to the news of Neal's request by saying that he is under audit and that "until such time as I'm not under audit, I would not be inclined to" cooperate with the request.

Trump is able to voluntarily release his returns both to Congress and the public, even though every president's returns are automatically placed under audit during their tenure in office.

The Treasury Department, which oversees the IRS and is headed by Mnuchin, a close Trump ally, is expected to fight the request in court. Mnuchin has said in the past that he will "review any request with the Treasury General Counsel for legality."

However, at a recent appearance before Neal's committee last month, Mnuchin said that the IRS commissioner, not the Treasury secretary himself, would make a determination over the request.

The businesses tax returns Neal requested include the trust that Trump placed much of his business interest into when he took office, as well as other holding companies associated with him and his golf club in Bedminster, New Jersey.

In addition to the tax returns, Neal requested any additional documents related to the filings, as well as a statement from the IRS if Trump or one of his businesses did not file taxes for a given year. Neal also asked the tax collection agency to clarify whether Trump was under audit for the years requested, which date from 2013 through 2018.

Congressional Republicans hammered the request as “weaponizing” the tax code.

“Weaponizing our nation’s tax code by targeting political foes sets a dangerous precedent and weakens Americans privacy right,” Rep. Kevin Brady, R-Texas, the top Republican on Neal’s committee, wrote in a letter to Mnuchin. “As you know, all Americans have a fundamental right to the privacy of the personal information found in their tax returns.”

"This is purely politically driven, what the Democrats in the House are trying to do on his income tax," said Sen. Chuck Grassley, R-Iowa, the chairman of the Senate Finance Committee.

Grassley has also said recently that he would also seek Trump's returns if Democrats are successful in their effort.