MOT centres will still be operating at a limited capacity as tests are increased this week, the head of the Driver and Vehicle Agency has said.
Testing resumed yesterday for additional vehicle categories such as four-year-old cars and motorbikes, and three-year-old light goods vehicles, heavy goods vehicles, trailers and buses.
It follows the resumption of testing for some vehicle groups last month.
MOT tests were suspended in January after faults were detected in some lifts and faced further disruption due to the Covid-19 pandemic.
Some centres were also used as coronavirus testing facilities.
The DVA issued temporary exemption certificates (TECs) for some vehicles to remain on the road.
In July it re-instated MOT testing for groups not able to avail of TECs such as taxis and buses due a first-time test.
Individual Vehicle Approval (IVA) testing for priority vehicles was also restored to ensure continued support for areas such as the health service.
Jeremy Logan, acting chief executive of the DVA, said the service was still operating at only around a third of capacity due to the pandemic.
"At the minute we are working at a limited capacity across the centre network of approximately 30-35 per cent, based on the measures that we have had to adopt to comply with the public health advice and guidance on social distancing," he told BBC Radio Ulster's Good Morning Ulster programme.
"As restrictions relax we would hope to bring more vehicles forward, so some vehicles in October or November may be issued with a temporary exemption certificate.
"However, if we have the capacity to test those vehicles at that time, they will be issued with a reminder notice and at that stage they will be called forward for tests.
"So at this stage, the customer doesn't need to do anything, they will be notified by us if they are due for a test and if they are not due for a test and they are going have a temporary exemption certificate applied, that will be automatically applied by DVA and will be updated on the DVA system as well."
Mr Logan reminded drivers that there are no hard copies of TECs issued and so they should check online the status of their MOT requirements.