It is the last chance for leaders to pitch their case and pick holes in their opponent's case in a debate before Saturday's election.
It will be too late for many voters - as of this afternoon 674,000 people had already voted.
The leaders have been fairly evenly matched in previous debates.
English said it was an opportunity to set out the case for voting for National.
"We're still three days and hundreds of thousands of people still to vote. So we'll be putting the choice to them very clearly."
Ardern said she would have the same approach as the first three debates.
"Just make sure I lay out the case for change and how important it is with just two and a half days left till the election for everyone to use their voice."
Since the last televised debate two weeks ago, Ardern has had to negotiate a U-turn on one of her first major decisions as Labour leader - the possibility of introducing new taxes such as a more comprehensive capital gains tax, a wealth tax and land tax in a first term Labour Government.
After National's concerted attacks on the uncertainty of Labour's policies, Ardern backtracked and announced last week no new taxes would be implemented until at least 2021 - after a further election.
Labour has accused National of circulating 'fake news' about Labour's numbers and its tax policy, including that Labour will increase income taxes.
English has denied that is wrong, saying under Labour people will pay $1000 more in taxes than under National. "From 1 April next year, Labour will be raising income taxes."
The day of the last debate, National's finance spokesman Steven Joyce had claimed there was an $11.7 billion hole in Labour's fiscal plan.
Ardern said she hoped English and National would not use any "misinformation" such as the $1.7 billion hole and Labour's tax plans.
"People want to hear a debate on the issues and that means the issues as they stand - not fake news."
Labour and successive economists have also rejected the hole - but English has continued to maintain Labour will have no money for budget increases in any areas other than health and education.
English has also defended National's claims Labour would increase income taxes, saying that from April next year a worker on the average wage would get $1000 a year less in income taxes under Labour than under National.
Both leaders spent the day campaigning in Auckland - for Ardern that was a visit to pack food boxes at Mangere Budgeting Service followed by a rally organised by First Union.
English's day was a stark contrast - he visited staff at the headquarters of three major corporates, Vodafone, ASB and Minter Ellison Rudd Watts and went for a walkabout along the Viaduct Harbour.
English denied it showed a difference in the campaigns, saying his own trail had taken him everywhere from welfare centres to workplaces. He said it was the probably the first time he had visited corporate offices on the trail, but there were votes there as well and he wanted to speak to as many people as possible.
