Just 24 new cars were sold in Northern Ireland in April, according to figures compiled by the Society of Motor Manufacturers and Traders (SMMT).
Car show rooms were closed during April as a result of coronavirus.
That meant sales collapsed by more than 99% when compared to the 4060 new cars sold in the same month last year.
Across the UK as a whole 4,321 cars were registered, the lowest monthly level since 1946.
The SMMT said that of the UK registrations made last month, 70% were by companies buying for their fleets.
The cars would most likely have been on order before the lockdown, said Mike Hawes, SMMT chief executive.
"If you are told to close all your car showrooms for the entirety of April it's no surprise sales are almost non-existent," he told the BBC.
The industry body said it now expects 1.68m new car registrations in 2020 compared with 2.3m in 2019.
Staff at some UK car manufacturers began returning to work this week, although the start of full production is a long way off, Mr Hawes said.
The supply chain is also starting to re-open.
"Manufacturers are trying to figure out how to start operations in a safe environment," he said.
"But it will be slow and production will be ramped up very slowly," he added.