Many centres nationally have little availability for February and March.
Due to the pandemic, extensions were given to motorists, but that has led to a backlog of testing.
Applus is recommending drivers check the website regularly for cancellations.
Sinn Fein's transport spokesperson, Darren O'Rourke, says there needs to be more capacity in the NCT system:
"It is important that people are aware in the first instance of the types of waiting periods. But it's important that those waiting periods are reduced and that every effort is made because there are implications for missed NCT dates, there are implications in terms of insurance, in terms of driver and road safety."
