As reported by n-tv and Handelsblatt the attorney general of Frankfurt authorised raids on offices in the Commerzbank headquarters as well as 3 private houses of accused individuals in the second week of November. The raid was based on the suspicion that Commerzbank evaded taxes by Cum-Ex trading in the past.
The attorney general claims investigations showed multi-billion Euro deals closed between 2006 and 2010 which evaded taxes of about 40 million Euros. Cum-Ex trades are share transactions around the dividend record date in which a share is moved quickly between several owners to disguise the actual owner when the dividend is distributed ((http://www.ey.com/Publication/vwLUAssets/EY-tax-controversy-news-alert-investigations-against-banks-en/$FILE/EY-tax-controversy-news-alert-investigations-against-banks-en.pdf)). In a second step the owners claimed back the dividend tax multiple times, while it was only paid once ((http://www.n-tv.de/wirtschaft/Steuerfahnder-durchsuchen-Commerzbank-article20127078.html)). Although first warnings about this practise arose in 1992 it took the German government until 2012 to prohibit Cum-Ex trading. According to Die Zeit at least 31.8 billion in taxes have been evaded in that timeframe. As a consequence of the Cum-Ex scandal Hypovereinsbank, HSH Nordbank and LBBW paid back 500 million Euros ((https://www.tagesschau.de/wirtschaft/cum-ex-macquarie-101.html)). Furthermore, the small Maple Bank had to file for bankruptcy due to a reclaim of 100 million Euros ((http://www.faz.net/aktuell/finanzen/bafin-verlangt-auskunft-ueber-cum-ex-geschaefte-14092916.html)). Parts of the paybacks were paid under reserve, as it has not yet legally been decided whether historic Cum-Ex trades are considered illegal.
According to Commerzbank’s own statements they initiated an internal examination of all stock dealings between 2003 and 2011, while providing results periodically to the authorities ((http://www.n-tv.de/wirtschaft/Steuerfahnder-durchsuchen-Commerzbank-article20127078.html)). It is unclear if this initiated the investigations.