The contest for party leader was triggered when Diane James gave up the leadership last month, just 18 days after being elected to replace Nigel Farage.
She subsequently said her relationship with Ukip had become “increasingly difficult” and quit the party.
Mr Farage returned as interim leader just months after announcing his resignation because he wanted to “get my life back”.
The leadership contest took a bizarre twist when early frontrunner Steven Woolfe quit the race - and later the party - following a fracas with a fellow MEP.
Ukip’s only MP has said he hopes the announcement of a new leader will provide the opportunity to “reset” the party.
North West England MEP Mr Nuttall has vowed to press Theresa May to give Mr Farage a seat in the House of Lords if he is elected leader.
He told the Sunday Telegraph it was “unfair and obscene” that the Government had not created a single Ukip peer.
During his campaign for the leadership, Mr Nuttall also set out plans to target disillusioned voters in Labour heartlands in a bid to improve Ukip’s presence at Westminster.
“We have this fantastic opportunity, which we’ve never had before to this extent, to move into Labour working-class communities and mop up votes,” he said.
“I think in some of these communities we can replace the Labour Party in the next five years and become the patriotic party of the working people.”
He added: “You’ve got a Labour Party whose leader refuses to sing the national anthem, whose shadow foreign secretary sneers at the flag, whose shadow chancellor says nice things about the IRA. That isn’t going to chime well with working-class people.”
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