Tax authorities have concluded that Nissan Motor Co. failed to pay tax on ¥150 million it had booked as business expenditures in the three years through March 2014, when Carlos Ghosn served as CEO and chairman, sources close to the matter said Tuesday.

The Tokyo Regional Taxation Bureau apparently determined that the sum should not have been treated as tax-deductible business expenses as Ghosn is suspected of using the company's money for private purposes.

For the undeclared tax over the three years, Nissan has been slapped with penalties of tens of millions of yen, the sources said, adding that the automaker could be taxed more as the bureau's investigations continue.