34,000 car owners have had their NCT certificates revoked.
The National Car Testing Service says some customers were wrongly provided with a two year cert instead of a one year one.
A system error has caused 34,000 NCT certs to be issued incorrectly in the last 12 months.
The issue only relates to cars that were over 10 years old at the time of their last test and which had their NCT extended by 4 months due the pandemic.
These vehicles were given a cert valid for two years instead of one.
The incorrect certificates, issued at the time of the inspections, have been revoked and new NCT certs are being issued to all affected customers.
In a statement the NCT service says this should be complete by August.
Anyone who has purchased one of the affected vehicles with the expectation of a longer NCT certificate duration, will be offered a full free test if the vehicle is booked in in advance of its revised test due date.
The NCTS says it's taken all the necessary steps to correct this administrative error and that it will contact each affected customer directly.
