Boston City Hall's assessing chief on Tuesday voiced an ever-tightening timeline for Beacon Hill to act on the city's property tax plan, while also declining to share data that some skeptical officials have said could be key to moving the needle on the controversial bill.

Boston Mayor Michelle Wu and the City Council shipped the proposal to the State House this fall for a second time, seeking to temporarily shift more of the burden of city property taxes onto commercial taxpayers to lessen expected hikes for residential homeowners.

Assessing Commissioner Nicholas Ariniello said the "drop-dead date" for legislative action on the bill (H 5114) could be as soon as Monday, Dec. 9 because the City Council needs to take a followup vote on Wednesday, Dec. 11.

"So working backwards from that, I optimistically would place the governor's signature on the 10th, and then place the Senate's action on Monday the 9th. But maybe they could double up and do things on the same day," Ariniello said at a hearing of the City Council Ways and Means Committee.

A Dec. 11 council vote "is honestly, I think, the latest that we could push a vote anyway, to make sure that we still did everything that needs to happen to get bills printed," he said.

The home-rule petition cleared the House on Nov. 25 after it was held up the previous week by the objections of Norwell Rep. David DeCoste. Coming to the Senate floor Dec. 2, it was South Boston Sen. Nick Collins who pushed off action until the following session, which is scheduled for Thursday, Dec. 5.

At Tuesday's council hearing, Councillor Erin Murphy asked Ariniello to share the city's updated property valuation data -- something Collins also asked for during Monday's Senate session on the hill. Ariniello declined, saying that the state Department of Revenue had not yet signed off on the numbers, and premature release of the figures would be "creating a situation for people to poke and create uncertainty."

"And I know it's been reported that the State House held off on a vote yesterday because they're waiting for the real numbers, the data, right? So what models, assumptions, data sources are we using?" Murphy asked during the hearing.

"The State House question I honestly can't answer, as to their motives," Ariniello replied.

He added, "The numbers that we're dealing with now are the final absolute precise numbers from the state in getting that approval. And because we don't have those, releasing anything that is more than the general economic trends ... is just creating a situation for people to poke and create uncertainty when we are so close to actually having final numbers."

Collins said the Senate should gain access to Boston's new data before voting on the bill. He said the city submitted its new valuations to the Department of Revenue for certification on Thanksgiving Eve.

In a statement after Tuesday's council hearing, Collins said: "Though city officials again refused to share the data on new valuations submitted to the state ... they did indicate they anticipate a surplus from the new valuations. Surplus funds should be directed toward residential tax relief, particularly for our seniors."

Earlier in its Tuesday sitting, the City Council budget panel heard from Boston Municipal Research Bureau interim President Martha Walz about the think tank's report on "Diversifying Boston's Revenue," which was released Nov. 12. Around 70 percent of the city budget is currently funded by property taxes, which Walz said makes Boston "uniquely dependent on the property tax, compared to other major cities across America."

Councillors and Walz spitballed some possible ways to raise new revenues and lessen the city's dependence on real estate taxes, including ideas contained in the BMRB report -- like charging for residential parking permits or imposing a local tax on tickets to sports games.

Councillor John FitzGerald floated the idea of a local sales tax on non-essential goods, something New York City has; or an excise and registration on electric scooters and bikes; or a local tax on sports betting, charged by geolocating where a person's cellphone is located when a bet is placed.

"And again, these are thrown out there without understanding who is going to be paying. And I don't want anyone to get their feathers ruffled at the moment, right? These are just ideas that are out there," FitzGerald said.