The use of Employee Benefit Trusts during Sir David Murray's tenure as owner of the now defunct 'oldco' Rangers was the subject of a long-running probe which ended earlier this year.
Her Majesty's Revenue and Customs (HMRC) are appealing a tribunal ruling which said some payments made to players through EBTs were taxable but that many of them could be described as loans, as the club had argued.
Murray, meanwhile, in November instructed legal advisors to submit a complaint to the Crown Office regarding the publication of information relating to his tax affairs.
And a police spokeswoman said: "Following instructions from the Crown Office, an investigation is ongoing into the circumstances surrounding the alleged leaking of confidential information relating to the Rangers tax case.
"It would be inappropriate to comment further at this time."