Two thirds of retailers have not paid their rent this month, and almost half of commercial rents overall are still due, says a property software firm.
The data comes from property software firm Re Leased, and is based on reconciled rent invoices from clients with an 1 April due date.
Re Leased chief executive Tom Wallace said the data provided an insight into just how hard the lockdown had hit commercial tenants and landlords.
"It was very sudden, it all happened very quickly. February rents were normal and then we've seen big impacts immediately in March and April.
"Once the lockdown happened, we weren't surprised to see the impact, but we were surprised to see how fast and how deep it happened - from one month to the next a drop to a third of the rents paid in retail is a massive hit with very little warning."
Of the total rent due on 1 April, 6.3 percent of it had been credited or written off by April 13 - in a regular month that figure was usually 1 percent.
Mr Wallace said that reflected the increasing rent relief agreements around the country, or payments written off because landlords knew they would not come.
He said that proportion was likely to rise as overall things were unlikely to improve.
"We'll be watching our data really closely as the government allows certain businesses to go back into trading to see how they recover. But we certainly think this impact will continue in the short term and probably will have a decent impact in the mid to long term as well."
He said landlords needed more support from the government.
"They've taken a huge impact themselves on their own businesses… there's a bit of a myth that they're all big businesses with huge assets and that is the case in some places, but they're also family trusts, charities, they have payroll, their own expenses and mortgages to pay… they're hurting too."
The Property Council agreed, saying the government measures so far would not be enough to cushion the blow for the $145 billion commercial property sector.
Chief executive Leonie Freeman said concerns about the impacts of non-payment remained.
"The challenges facing business are vast and uncharted… extending timeframes required before landlords can cancel leases and mortgagees can exercise their rights will give tenants and landlords some additional time to resolve contractual issues. However, we remain concerned that the risks involved in non-payment of rent could have wider implications for the property industry and the wider economy.
"In our discussions with government, we proposed a support package for commercial tenants facing a 50 percent loss of revenue. This comprised multiple components that would have provided immediate relief to tenants so they could continue to meet their contractual obligations.
"Proposals included a deferral of rent by landlords facilitated by the tax system and a targeted rent tax credit for tenants with direct financial assistance via a mechanism similar to the government's wage subsidy"
She said if left as is, there could be flow-on effects for the economy.
"Our members, many of whom are the long-term investors who develop new real estate, are telling us that without more certainty around their cashflow, they face having to halt construction on planned projects. This could have a devastating effect on the property and construction sector, with hundreds of thousands of New Zealanders relying on these projects to stay in work and in business."