With no return to devolved government, the NI secretary must call an election within 12 weeks.
Northern Ireland is on course for an assembly election after politicians missed the deadline set by Westminster for restoring devolved government.
Secretary of State Chris Heaton-Harris now must call an election to be held within 12 weeks.
He has pledged to do this on Friday, rather than try to delay it or avoid it with fresh legislation at Westminster.
The most likely date is 15 December, although a date for a poll does not have to be set immediately.
Mr Heaton-Harris is expected to lay out the next steps later on Friday.
The Democratic Unionist Party (DUP) is blocking the restoration of power-sharing in its protest against the post-Brexit trading arrangements called the Northern Ireland Protocol.
Unionist politicians argue the protocol undermines Northern Ireland’s position in the UK.
It keeps Northern Ireland aligned with some EU trade rules to ensure goods can move freely across the Irish land border.
Analysis: Campaign trail leads to Christmas
by Darran Marshall, BBC News NI political correspondent
Chris Heaton-Harris had repeatedly pledged to call a fresh election if the devolved institutions were not reformed.
We can expect him to move quickly. A formal announcement may come as early as lunch time on Friday.
Politicians at Stormont had argued that a new election would not solve the impasse over the Northern Ireland Protocol.
But they are now resigned to the fact they’ll be hitting the campaign trail before Christmas.
As it stands, it is far from clear that the power-sharing government will return on the other side of an election.
The DUP withdrew from the Northern Ireland Executive in February, with ministers remaining in post but with only limited powers.
The executive is made up of ministers from the largest parties under a power-sharing arrangement, and is designed to ensure unionists and nationalists govern together.
On Thursday, politicians failed in last-ditch efforts to restore devolved government ahead of the deadline.
Assembly members met at Stormont as Sinn Féin, which won the largest number of seats in the last assembly election in May, called for the DUP to end its protest.
The party’s vice-president Michelle O’Neill, who is entitled to the first minister position after Sinn Féin’s success in May’s election, accused DUP leader Sir Jeffrey Donaldson of a “failure of leadership”.
What happens next?
With the deadline passed, the secretary of state must call an election “as soon as is practicable” – to be held within 12 weeks.
Chris Heaton-Harris, who has been in office since 6 September, has consistently said he will call one after the deadline passes.
Stormont’s caretaker ministers were removed from office as of midnight and senior civil servants are now in charge.
The assembly – which has been meeting only for special recalls since May’s election – has also been dissolved.
As the DUP has said it will continue its protest against the Northern Ireland Protocol, the election is unlikely in itself to break the stalemate.
So Northern Ireland could be set for further cycles of negotiations, up to 24 weeks, and future elections, until a resolution is found or the law is changed.
But the DUP denounced the assembly meeting as a “flawed and failed attempt” to restore power-sharing.
The meeting failed to elect a Speaker, or the first and deputy first ministers, so no government could be formed.
It is the fourth time the assembly has met and failed to elect a Speaker since May’s election.
Prime Minister Rishi Sunak had urged the DUP to return to Stormont, with an official spokesman saying “the people of Northern Ireland deserve a fully functioning and locally-elected executive which can respond to the issues facing the communities there”.
Irish Tánaiste (deputy prime minister) Leo Varadkar described the situation as regrettable, urging all parties, particularly the DUP, to “honour their mandate”.