Car maker Nissan is recalling 1.2 million vehicles in Japan produced between October 2014 and September this year for re-inspection because they did not go through the proper final checks.
A team, including an independent third party, is investigating the cause of the oversight and has promised to prevent it from happening again.
The problem does not affect Nissan vehicles sold outside Japan.
The failure is not believed to have affected vehicle safety as they were final-stage checks, according to the Yokohama-based maker of the March subcompact, Leaf electric car and Infiniti luxury models.
Nissan chief executive Hiroto Saikawa told reporters the oversight occurred at all six Nissan plants in Japan.
He acknowledged not enough had been done to ensure staff were aware of inspection requirements.
He estimated the recalls and re-inspections would cost Nissan about 25 billion yen (£165 million), but stressed final costs are still unclear.
The inspection oversight is an embarrassment for Nissan.
The car giant temporarily stopped registering new vehicles in Japan last week, after the government notified the company it had noticed inspection irregularities.
The car industry has been hit by a series of recent scandals.
Germany's Volkswagen AG acknowledged in 2015 that it had equipped its diesel cars with illegal software that enabled cheating on US emissions tests.
Volkswagen has agreed to more than £15 billion in fines and civil settlements over the scandal.