Legislation was enacted in 2012 to close the legal loophole exploited by these transactions, and in 2021, the Federal Court ruled that Cum-Ex transactions constitute tax evasion.

Steck is accused of committing eight acts of severe tax evasion between 2007 and 2015, defrauding the German government of a total of 428 million euros.

Among the allegations, Steck is said to have defrauded the state of 50 million euros through illegal 'Cum-ex' stock transactions.

Steck, who confessed to his involvement in the scheme in 2016, has served as a key witness in several trials, providing extensive testimony that has been crucial in indicting other defendants.

This scandal primarily affected Germany, with total losses for the German government estimated in the tens of billions of euros.

The trial of Kai-Uwe Steck, a prominent lawyer and key witness in the Cum-Ex tax scandal, began on November 21, 2024, in Bonn, where he faces serious charges of tax evasion.

Despite his cooperation with authorities, which has led to multiple investigations and convictions, Steck has not received guarantees against prosecution.

The scheme exploited a tax law loophole by allowing investors to swap shares around dividend payment dates, enabling them to claim tax refunds for taxes they never paid.

Although Steck previously expressed a willingness to return 50 million euros he earned from the scheme, he has only repaid 11 million euros to date.

Steck's defense attorney has accused the Cologne public prosecutor's office of treating him unfairly and failing to uphold promises made during negotiations.

The Cum-Ex scandal, which peaked between 2006 and 2011, involved a complex network of financial misconduct that has drawn significant public and legal scrutiny.

The trial is expected to last for 24 sessions and may set precedents for numerous other ongoing investigations involving approximately 1,700 other suspects.