Australians on low and middle incomes could still get the extra tax relief promised by the coalition this year even if it doesn't clear parliament by tax time.
But it remains to be seen if the proposed tax cuts will pass parliament at all, with key crossbench senators still to pledge their support for the plan.
Prime Minister Scott Morrison and Treasurer Josh Frydenberg have made legislating the tax cuts their top priority, but are at the mercy of the Australian Electoral Commission on when they can bring parliament back.
Parliament can't sit until the AEC returns the election writ to the governor general, which is due by June 28.
In a helpful twist for the government, the Australian Tax Office says it can retrospectively amend tax assessments to provide cuts if the laws pass after June.
The agency could also make administrative changes to provide tax cuts, if Labor backs them.
"We would be able to update the tax withholding schedules, to allow the tax cuts to be reflected in people's take home pay," the ATO says on its website.
Labor has backed the coalition's promised doubling of a tax offset for low and middle income earners.
Under the reform, people earning up to $37,000 would pay $255 less in tax, with that saving increased incrementally for people earning between $37,000 and $48,000.
People earning between $48,000 and $90,000 would score a maximum refund of $1080, with the offset then gradually dialled back to zero for people earning up to $126,000.
But Labor has taken issue with later stages of the coalition's tax plan, set to be fully rolled out by mid-2025, including flattening the marginal tax rate to 30 per cent for everyone earning between $45,000 and $200,000.
Mr Frydenberg says the coalition's tax plans are a package deal.
"It is important that this is dealt with as a package, because we are talking not just about immediate tax relief, but we're also talking about long-term structural reform," he told reporters in Canberra.
Labor's Andrew Leigh says his party will decide where it stands on the package in the aftermath of its election defeat through its "normal consultative channels".
"We don't suddenly turn into a rubber stamp for the Liberals just because we lost an election," he told ABC Radio National.
Lacking support from Labor would require the government to rally crossbench votes.
Greens leader Richard Di Natale says the minor party won't support income tax cuts that aren't targetted at people earning the least.
"We're not going to support tax cuts to people on half a million dollars," he told ABC Radio.
The party held onto all of its six Senate seats up for re-election, taking the Greens' total to nine.
Reserve Bank of Australia Governor Philip Lowe says not rolling out the doubled tax offset this year would mean household income growth would be 0.3 per cent lower than it could be.
"That is moving in the wrong direction," he said after a speech in Brisbane on Tuesday.
