The fate of the Turnbull government's $50 billion 10-year company tax cut package remains unclear amid last-ditch negotiations with crossbench senator Nick Xenophon.
The Senate had been expected to debate the measures into the wee hours of Friday morning.
But instead the upper house adjourned just after midnight, following a marathon debate on controversial changes to race-hate speech laws.
The government's bid to re-word section 18C of the Racial Discrimination Act was killed off by a Labor amendment at about 10.30pm (AEDT) on Thursday but the government dragged out the debate for a further hour and half before parking the gutted human rights bill.
Labor accused the government of filibustering in order to cut a deal.
The Senate is scheduled to resume sitting at 9am on Friday, however it's not certain whether it will return to the human rights bill, which will tweak the Human Rights Commission's complaints process, or move straight on to the company tax cuts draft laws.
Senator Xenophon arrived back in Canberra on Thursday night after attending a funeral in Adelaide.
His bloc of three senators back a reduction for businesses with a $10 million turnover.
Fellow crossbencher Derryn Hinch was also backing a reduction up to $10 million but had changed his mind on Thursday night, supporting tax cuts for businesses with a turnover of up to $50 million.
Pauline Hanson's bloc of four senators also support a reduction up to $50 million while the government can expect support from crossbenchers David Leyonhjelm and Cory Bernardi.
Treasurer Scott Morrison was coy on the progress of negotiations insisting even a cut up to $10 million was a win.
There were 100,000 businesses with a turnover between $2 million and $10 million, which employ 2.2 million Australians, he said.
"At the very least, if that's what is achieved... then I would say that is a very, very good result for those 2.2 million Australians and I wouldn't dismiss it in the way that some might," Morrison told ABC TV.
"If the adage is that, in today's politics, it's 100 per cent of something or 100 per cent of nothing, then I don't think that's the practical way to approach politics."
Shadow Treasurer Chris Bowen said Labor has consistently supported a $2 million company threshold.
"The government is clearly scrambling," he told ABC TV.
The government wants the tax cuts voted on before parliament rises for a month-long break before the May budget.
The aim of the package is to get the tax rate down to 25 per cent for all businesses in a decade's time.
