A majority of lawmakers in both the House and in the Senate are now backing legislation that supporters say could bring in an additional $400 million in annual revenue for the state by raising a tax on some “megacorporations.”

The legislation (H 3110 / S 2033) from Sen. Jason Lewis of Winchester and Rep. Carlos González of Springfield would increase the share of excess foreign profits that Massachusetts taxes, building off a federal government formula called Global Intangible Low-Taxed Income or GILTI.

Massachusetts currently taxes 5% of GILTI when calculating global corporations’ state taxes. The Lewis/González legislation would raise that share to 50%. Massachusetts and Connecticut tax GILTI at 5% while the other four New England states have a 50% rate in place.

MassBudget Policy Director Phineas Baxandall said Tuesday that less than 0.5% of the more than 1.5 million corporations that filed taxes with the U.S. Internal Revenue Service in 2021 reported any amount of GILTI, and that 93% of all GILTI reported that year was earned by corporations with more than $2.5 billion in assets. He said raising the state GILTI rate would bring in additional revenue by affecting only companies large enough to use the type of tax avoidance schemes GILTI seeks to address.

“I know that as this issue heats up, there are going to be folks who are going to paint a different picture of who GILTI affects. But the statistical reality is that this is something which impacts overwhelmingly really global megacorporations,” he said. “And it’s important to keep that in mind.”

Within each branch of the Legislature, there is majority support for the Lewis/González bill. Eighty-two of 158 current representatives have signed on as cosponsors, as have 21 of 40 senators including Republican Patrick O’Connor of Weymouth.

While the support levels are high, it’s up to top Democrats in the Legislature to decide if and when the bill might emerge for floor votes, and legislative leaders have not signaled any plans for the bill, which awaits its initial public hearing. Top lawmakers this budget cycle have celebrated the fact that their budgets do not include tax increases, and state tax collections are exceeding expectations and have been sufficient to stock a more-than-$8 billion rainy day fund.

Speaking at a Massachusetts Budget and Policy Center event Tuesday, Lewis said the legislation was a “no-brainer” for him since it brings in additional revenue “in a way that is equitable.”

“We don’t want to raise taxes on lower- and middle-income working families and small businesses. They are struggling. We know cost of living is a major issue that we’re facing in Massachusetts. But we are fortunate to be a state that has some very wealthy households, has some very successful multinational corporations that operate here, and then there’s no question in my mind this tiny number of very large, very profitable multinational corporations can afford to pay a little bit more in state taxes,” Lewis said. “I don’t think it’s going to have any impacts their operations here. And those hundreds of millions in revenue will enable us to make important investments in the people of Massachusetts.”

The Lewis/González bill is before the Joint Committee on Revenue, which is newly under the leadership of chairs Rep. Adrian Madaro and Sen. Jamie Eldridge, but it has not yet been scheduled for a hearing. Eldridge is one of the senators who cosponsored the bill.

The Institute of Taxation and Economic Policies estimates that Massachusetts’ current 5% GILTI rate generates about $65 million annually. MassBudget scaled that up to project what would happen under a 50% GILTI rate and arrived at a potential net revenue gain of $585 million annually.

But anticipating that many corporations may choose the option of filing their taxes under a set of rules called “worldwide combined reporting,” which already accounts for shifted offshore profits, MassBudget’s analysis determined that $467 million is the “likely ceiling for new revenues resulting from a shift to requiring 50% GILTI inclusion” and that $400 million annually is the best estimate of actual revenue that could be realized, given other tax avoidance mechanisms that may remain available to affected companies.

MassBudget President Viviana Abreu-Hernández said the time is ripe for Massachusetts to “raise additional state revenue to protect critical programs that provide families across the state access to health care, food, housing and more” as D.C. Republicans move to cut federal spending and support to states.

“With expected federal cuts, to the tune of $700 billion from Medicaid alone, states must make up the difference to help prevent devastating cuts to healthcare and other critical public services,” she said in a statement. “MA needs additional revenue, and lawmakers recognize that we can raise it while making our tax structure more fair for small, local businesses.”

But the uncertainty in Washington was one of the reasons the head of an influential business-backed group previously cautioned against making a “major corporate tax increase” that could “clearly run counter to the relatively broad consensus we’ve seen over the last few years of trying to increase the state’s competitiveness.”

“Given the uncertainty with what the feds are going to do, it doesn’t make any sense to contemplate a change at the state level,” Mass. Taxpayers Foundation President Doug Howgate said in February. “I don’t think it makes sense to move forward with a proposal like that at all.”

Raise Up Massachusetts, the influential coalition that shepherded passage of the income surtax on wealthier Massachusetts households and has won minimum wage increases, is backing the GILTI proposal and has dubbed it the “Corporate Fair Share” proposal.