Investigators search Deutsche Bank's headquarters over legacy tax trades

By Tom Sims and Matthias Inverardi

FRANKFURT, July 22 (Reuters) - German prosecutors were searching offices at Deutsche Bank's headquarters in Frankfurt on Wednesday as they investigate alleged fraudulent tax transactions at the lender's Postbank unit years earlier.

The bank confirmed that Duesseldorf prosecutors were at its office in the city, and that the probe related to transactions at its Postbank division between 2008 and 2010.

"Deutsche Bank is being searched as a third party in this matter and we are cooperating fully," Deutsche Bank said, declining to comment further.

Duesseldorf prosecutors did not immediately respond to a request for comment.

PROBE RELATES TO 'CUM-CUM' TRADES, SOURCE SAYS

A person familiar with the matter said the search involved so-called cum-cum trades, confirming German media reports.

Such schemes involved trading in stocks of German companies around dividend payout days, which authorities say amounted to tax fraud.

The transactions flourished during the financial crisis, and authorities estimated they stripped state coffers of billions. A years-long crackdown has since sought to claw back the money.

The alleged roles of German financial firms in cum-cum trades, as well as in related cum-ex deals, are likely to cost the industry around €7 billion ($8 billion), German financial watchdog BaFin said last week, citing a survey.

It marks the third time that prosecutors are known to have searched Deutsche Bank this year. A case earlier this year related to money laundering, and a second last week was related to its retail bank.

(Reporting by Tom Sims, Writing by Ludwig Burger, Editing by Miranda Murray, Jan Harvey and Sabine Wollrab)