Macquarie Group's current and future chief executives are expected to be interviewed by German police over the bank's involvement in a share trading case.
In a statement to the ASX on Friday, Macquarie said Nicholas Moore and incoming chief executive officer Shemara Wikramanayake are likely to be classified as "persons of interest or suspects" in the investigation.
Macquarie were lenders to a group of investment funds in 2011 which were seeking to obtain benefits for their investors from dividend withholding tax credits.
The investor's claims were refused, the bank said, adding it believed it was acting lawfully at the time.
The transactions are being investigated by the Cologne Prosecutors Office and, although staff have yet to be approached, Macquarie said, it understands up to 30 people including Mr Moore and Ms Wikramanayake may be interviewed.
The same transactions are the subject of a civil case currently being heard in the Munich District Court.
Two investors have already sued the Swiss bank, which introduced them to the investment, Macquarie says.
"They and other investors have now sold their claims to a German litigation Special Purpose Vehicle controlled by the same lawyer who acted in the litigation against the Swiss bank," it said.
That entity filed a claim earlier this year seeking 30 million euros ($A48.42 million) in damages.
Australia's largest investment bank says it "strongly disputes" the claim.
"(Macquarie) did not arrange, advise or otherwise engage with the investors, who were high net-worth individuals with their own advisors," it said.
The scandal has embroiled scores of German and international banks and has reportedly denied the German government billions in revenue.
The legal loophole, which allowed multiple tax credits on a dividend only paid once, was scrapped in 2012.
Macquarie Group shares were down 32 cents, or 0.25 per cent, at $127.43 at 1224 AEST.
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