AUGUSTA — Gov. Janet Mills signed an emergency $473 million heating and energy relief bill Wednesday afternoon that includes a round of $450 checks to most taxpayers.

Both the House and Senate passed the bill with enough support to enact it as an emergency measure. At least two-thirds of both chambers must support legislation for it to take effect immediately.

Mills announced soon after the votes that she had signed the bill into law. The state could begin mailing $450 relief checks later this month.

“With high energy prices causing real hardship, this emergency measure will ease the financial burden on Maine people by putting money back into their pockets and ensure that our most vulnerable citizens are able to stay warm this winter,” Mills said in a written statement.

“I thank the Legislature for its strong, bipartisan vote, and I look forward to continuing to work with them to implement long-term solutions that will bring down energy costs, improve energy efficiency, and reduce Maine’s highest-in-the-nation dependence on expensive and harmful fossil fuels.”

The Senate voted 24-10 in favor of the bill and the House voted 114-29 for passage. Several floor amendments were rejected Wednesday morning before the final votes.

The heating and rental assistance package was the first order of business as lawmakers returned to Augusta to kick off the 131st legislative session in earnest.

The emergency bill, which also will provide tens of millions of dollars in heating aid for low- and middle-income households and millions more for emergency housing and shelter, needed two-thirds support in both the House and Senate. It had strong bipartisan support in the House last month, but was blocked by Senate Republicans, who demanded a public hearing.

That hearing was held in late December and Senate Minority Leader Trey Stewart, R-Presque Isle, announced that some of his caucus members would now support the bill, even though no changes were made to the original proposal negotiated by Gov. Janet Mills and party leaders in each chamber.

This winter’s heating and energy prices — as well as inflation generally — are expected to stretch or exceed household budgets and deplete existing home heating assistance programs. Such concerns were expressed repeatedly by both Republicans and Democrats during the campaign season.

The winter energy relief proposal, funded with surplus money, will provide $450 checks to roughly 880,000 income-eligible taxpayers. Checks are to be automatically mailed to individual taxpayers who earned up to $100,000 in 2021, heads of households who earned $150,000 and married couples who earned up to $200,000.

The winter energy relief payments make up about $389 million of the $473 million package.

Kirsten Figueroa, the commissioner of the Department of Administrative and Financial Affairs, said last month that the program is identical to the previous round of $850 checks and will be sent to the same pool of qualifying taxpayers, which should allow the state to issue them more quickly.

Figueroa said with approval on Jan. 4, the state would begin issuing checks by the end of January and that all of the checks should be issued by the end of March.

The bill also contains $4 million to finish the first round of inflation relief checks.

Figueroa said that nearly 13,500 eligible taxpayers are awaiting those $850 checks because initial estimates of the funds required were too low. She said the money allocated assumed a 4% increase in tax filings to qualify for the checks, but the increase was actually 12%, driven primarily by people who don’t normally file tax returns.

The new law also adds $40 million to the Low Income Home Energy Assistance Program (LIHEAP) and another $10 million in emergency heating assistance for households that don’t qualify for the low income program.

And it includes an additional $21 million for housing assistance. About $6 million of that funding is being earmarked for applications for federal emergency rental assistance that were pending when the state shut down the program on Sept. 29.

To pass, the bill needed the support of 101 House members and 24 senators.

Republican legislators offered four amendments, including two proposing a gas tax holiday. All were rejected.

Rep. Laurel Libby, R-Auburn, offered an amendment to eliminate the $450 rebate checks and instead adopt a sales tax holiday for roughly three months, arguing that it would help more Mainers than in the income targeted checks.

While acknowledging that “you’d have to be crazy” not to want a $450 check, Libby blamed pandemic-era stimulus and relief checks issued under both Trump and Biden for fueling inflation. Instead, she said, lawmakers should cut taxes for working Mainers.

“Why, when we have repeatedly had a surplus at the state level, do we not cut taxes instead of writing checks, thus leaving more money in the pockets of hardworking Mainers in the first place?” Libby said.

Sen. Eric Brakey, R-Auburn, offered a similar amendment in the Senate, arguing that people have become too reliant on government checks during the pandemic.

Brakey questioned whether the bill would lead to what’s known as a universal basic income program where “people can wait more and more for the next round of checks to be sent out.”

“I’m somewhat concerned about the pattern that we’re establishing here,” he said. “There is much to debate about a policy like (universal basic income) and I hope we would debate that policy and not accidentally stumble into it.”

Sen. Maryanne Moore, R-Calais, also tried to eliminate the relief checks and instead offer one-time, $450 vouchers for heating fuel.

Sen. James Libby, R-Standish, also offered an unsuccessful amendment to sunset a provision of the bill that would allow the Maine Department of Environmental Protection commissioner to suspend sulfur requirements in fuels.

A competing proposal announced in a press conference last month by Sen. Rick Bennett, R-Oxford, and Sen. Nicole Grohoski, D-Ellsworth, was not offered in the first round of debates. That plan would have targeted relief checks to the lowest income Mainers, among other things.