The trial of former Nissan Motor Co boss Carlos Ghosn on charges of under-reporting his salary is expected to start in Tokyo in September.

Japan's public broadcaster NHK on Wednesday said Ghosn's first court appearance may be on May 23 as part of the preparations for the trial.

Ghosn was released on $US9 million ($A12.6 million) bail this month after spending more than 100 days in a Tokyo detention centre.

He faces charges of under-reporting his salary at Nissan by about $US82 million over nearly a decade.

Ghosn has said the charges are "meritless".

He was stripped of the role of Nissan chairman but remains a board member.