Mitsubishi made the allegation in a statement which gave details of these operations, uncovered in an internal investigation, reports Efe news.
The accusation follows other alleged irregularities in Nissan, which controls Mitsubishi.
It said the payment was made by NissanMitsubishi BV (NMBV), a 50-50 venture set up in the Netherlands in June 2017.
The payment was done on the basis of an agreement "concluded by a person who was not authorized to do so (and) no appropriate procedure was taken to pay any remuneration to Ghosn".
It was made as remuneration on the basis of an employment agreement that NMBV and Ghosn entered into to appoint him as managing director, the statement said.
On April 26, 2018, both Mitsubishi and Nissan had paid approximately 15.62 million euros in total to NMBV as a service fee.
The statement said the payment Ghosn received was "hidden" from Mitsubishi but was discovered through the disclosure of information by Nissan.
Mitsubishi also said it "will further investigate the cause and consider action to pursue liability against Ghosn in collaboration with Nissan".
Ghosn, who has been in detention in Tokyo since November 19, 2018, was chairman of both Nissan and Mitsubishi, but was removed from the positions after his arrest.
Tokyo prosecutors have accused Ghosn of under-reporting his income by tens of millions of dollars in documents to investors based on an understanding that he would receive them as post-retirement compensation as well as of breach of trust.