(CNN) Illinois Democrats approved a bill that would require presidential candidates to disclose their tax returns if they want their names to appear on the state's ballot.

The push from Illinois Democrats for President Donald Trump's taxes ahead of the 2020 presidential election comes as several other states are pursuing similar legislation -- and congressional Democrats are seeking to gain access to the President's tax returns under a 1924 provision in the Internal Revenue Code

As a candidate, and now as president, Trump has declined to release his tax returns, claiming he's prevented from doing so because he's under IRS audit. An audit, however, does not legally Trump bar from releasing his tax returns and has not stopped past presidents from doing so.

"Voters have a right to know a presidential candidate's conflicts of interests," Muñoz said in a statement on his website. "They have reasonably expected this disclosure for decades, and if candidates won't release the information willingly, then we need a law in place that requires it."

Since 2017, 18 state legislatures, including those in Illinois and New York, have introduced bills that would require presidential candidates to publicly disclose their tax returns to be on the ballot, according to the National Conference of State Legislatures

House Democrats in Washington formally requested the President's tax returns last week from the Internal Revenue Service, but Treasury Secretary Steven Mnuchin informed them on Wednesday that his department would be unable to comply with their deadline for Trump's tax return.

Under the bill approved Thursday, the Illinois secretary of state would post the tax returns on its website, with the candidate's personal information redacted. The bill would not apply to congressional or statewide candidates.

The measure was approved by the Illinois Democratic-controlled Senate, 36-19. The bill has moved to the Illinois House, where Democrats also hold the majority. CNN has reached out to Democratic Gov. J.B. Pritzker's office for comment of whether the governor supports the bill.

Republican state Sen. Dale Righter questioned the bill's constitutionality and called it "an embarrassing waste of the Senate's time" on Thursday, the Capitol News Illinois reported.