Photo: Diego M. Radzinschi/ALM

Clifford Chance's Frankfurt office was raided last Thursday by German authorities seeking files on a banking client that is caught up in the cum-ex tax saga.

The search and subsequent handing over of files was not against the firm itself, but rather ABN Amro, which the firm is advising in relation to cum-ex misconduct, according to a person with knowledge of the matter.

ABN Amro was also searched by prosecutors on Thursday. Another person familiar with the German legal market said that Clifford Chance lawyers helped block the search of the bank in November last year, which could result in an investigation by the prosecutor against the law firm.

In a statement, a Clifford Chance spokesperson said: "We are currently helping some clients who have received legal advice from third parties in the past to work through possible cum/ex matters. We can confirm that Clifford Chance has not given any opinions endorsing cum-ex structures in the past. Nor has any public prosecutor's office ever investigated our firm for promoting cum/ex models."

"Where we represent clients in criminal proceedings, as in the case reported, we exercise our clients' rights of defence with determination. Never before have Clifford Chance lawyers been accused of attempting to obstruct justice. We consider the accusations now made by the Cologne public prosecutor's office to be wholly unjustified."

The cum-ex tax scandal has clouded German commerce for several years and centres on transactions which were allegedly used by a number of banks to claim multiple tax refunds that had only been paid to the German authorities once, before a loophole allowing such practices was closed in 2012.

Last month, Freshfields Bruckhaus Deringer's former head of tax Ulf Johannemann had charges brought against him in relation to "serious tax evasion" for developing and advising on the so-called "cum-ex" transactions while "knowing the actual structure of the cum-ex transactions and deliberately issuing a maturity report in order to make the business seem supposedly legal".

Freshfields' Frankfurt office has been raided three times in relation to the scandal.

The Public Prosecutor's office in Cologne did not respond immediately to a request for comment.