Washington state lawmakers have taken a significant step toward enacting an income tax on high-income residents after the measure cleared its first major legislative hurdle in the Senate.

On Monday, Democrats advanced the so-called “millionaires tax” out of the Senate Ways and Means Committee, signalling momentum behind a proposal that would mark a historic shift in the state’s longstanding tax structure.

The legislation, embodied in Senate Bill 6346 and its House companion, House Bill 2724, would impose a 9.9 percent tax on adjusted gross income above $1 million, with the first revenues expected for the 2029 tax year.

Supporters say the levy would modernise Washington’s tax code, which currently lacks a broad-based personal income tax, and raise billions of dollars annually for priorities including tax relief, education, public services and social programmes.

Proponents also emphasise provisions that would eliminate the sales tax on personal hygiene products and expand credits for small businesses.

The committee vote came despite resistance from some quarters, including concerns about potential legal challenges and economic impacts.

Washington’s tax climate has historically eschewed personal income levies, and the state’s Supreme Court struck down a prior attempt to repeal the capital gains tax on similar grounds of tax structure and constitutional limits.

Unlike a voter-approved initiative, the Legislature’s power to amend its own 2024 ban on income taxes allows the measure to advance with a simple majority, bypassing more stringent voter requirements.

Governor Bob Ferguson, a Democrat, has expressed conditional support for an income tax on high earners but has called for adjustments to ensure the revenue delivers meaningful tax relief and supports working families.

Negotiations between the governor’s office and legislative leaders are ongoing, with disagreements over how much of the revenue should go toward rate reductions for low- and middle-income households.

Republican lawmakers have criticised the proposal as a break with Washington’s tax traditions and warned that it could discourage economic growth and drive high-income taxpayers out of the state.

They also argue the bill may set a precedent for broader taxation.

Legal experts predict the measure would face immediate constitutional challenges if passed, with opponents likely to argue that progressive income taxes are barred under longstanding state law.

Observers say the dispute could ultimately land before courts or the ballot box even if the Legislature approves the bill.

As the Legislature moves toward further hearings and floor votes, the debate over the income tax on higher earners highlights fundamental questions about tax fairness, revenue stability and the future of Washington’s fiscal policy.

With both chambers controlled by Democratic majorities and significant public attention on the measure’s economic implications, the path forward will shape fiscal debates across the state in the coming months.