Federal Labor wants more information from the coalition about promised tax cuts before it decides whether to back them.
Labor supports the first part of the government's tax plans, which will provide extra tax relief for low and middle-income earners.
But it is yet to decide whether it will back the later stage of the government's package - to flatten the tax system by mid-2024 - when it comes before parliament next month.
The coalition has ruled out breaking up the legislation, leaving Labor to mull whether it will back all of the package or none of it.
New shadow treasurer Jim Chalmers says the opposition is still waiting for the government to state what share of the extra tax relief in the package will go towards people on the nation's highest incomes.
"They've been unwilling to tell us that, and yet they want us to make a decision on it," he told ABC Radio on Monday.
"I think we need some more information from the government. We need to have more discussion on our end as well."
The issue will be canvassed when Labor leader Anthony Albanese's shadow cabinet meets for the first time in Brisbane on Tuesday.
"We'll come to a view well before the vote in the parliament in a month's time," Dr Chalmers said.
Mr Albanese has taken issue with the government telling Australians before the election that they would have access to the extra tax relief this tax time.
With federal parliament set to start on July 2, the tax cuts will now be dealt with after some people have started filing their returns.
"There is no reason why the parliament can't sit before July 1, sit for an hour, I've made the offer," he told ABC TV.
"The Senate, of course, I can't control, but we can put those tax cuts through in a day and it can be done efficiently."
Labor is also weighing up the future of the tax policies it took to the election, such as reigning in housing tax breaks and tax rebates for some shareholders.
"We'll take our time to work through those and which out which ones we want to keep and which ones we want to discard," Dr Chalmers said.
