Japanese media reports have said that the dates were changed to allow the maximum amount of cashing in on the stock prices, allowing Saikawa to receive tens of millions of yen (hundreds of thousands of dollars) in dubious compensation.
The latest development comes as former Nissan Chairman Carlos Ghosn is awaiting trial on charges of falsifying documents on deferred compensation and of breach of trust in allegedly diverting Nissan money for personal gain. He denies wrongdoing.
Saikawa blamed what he called "the Ghosn system" at Nissan for the payments, and said the system was being reviewed.
Saikawa succeeded Ghosn and in the past was closely allied with Ghosn, who led Nissan for two decades and made it one of the most successful automakers in the world.
Saikawa said he had left the task of overseeing the compensation system to Greg Kelly, a former board director who was arrested last year with Ghosn on financial misconduct allegations. Kelly has maintained he is innocent.
Since the arrests of Ghosn and Kelly, Nissan profits and sales have tumbled. Investors are also worried about Nissan's relationship with alliance partner Renault SA of France, which owns 43% of Nissan. Ghosn was sent in by Renault to lead Nissan, and in the years before his arrest had led both Renault and Nissan.
- AP