German prosecutors have searched over a dozen offices and homes across the country as part of their investigation into a massive tax fraud going back more than a decade, officials said Thursday.

The scheme involved so-called cum-ex transactions in which participants would lend each other shares so they could collect reimbursement for taxes they hadn’t paid, costing taxpayers across Europe billions of euros (dollars).

Frankfurt prosecutors said about 170 officers raided 19 premises in four German states Tuesday. In total, German authorities are conducting 10 separate investigations into cum-ex schemes, some of which involved bank employees.

After it was discovered, authorities closed legal loopholes that had made the scheme possible.

Separately, a court in Switzerland on Thursday convicted a former employee of Swiss private bank Sarasin of passing confidential client information to a journalist — blowing the lid on the cum-ex tax scheme.

The defendant, a German citizen, was sentenced to 13 months in prison and a fine of 20,400 Swiss francs ($19,960), suspended for two years, for “economic espionage” and attempted harassment, according to a statement by the Zurich regional court.

A German lawyer who used the documents in a civil case was acquitted of economic espionage. But the Zurich court found him guilty of inciting others to break Swiss banking law and sentenced him to a fine of 165,600 Swiss francs, suspended for two years. A third defendant, who also worked for Bank Sarasin, was also found guilty of incitement and sentenced to a suspended fine of 129,600 Swiss francs.

The verdicts can be appealed.

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