Shares were down 1.19% at midday in London, to change hands at Sfr14.91, biting into the 2.12% gains since the start of the year.
The Swiss bank on Friday said that tax investigations were launched in the U.K., France and the Netherlands. Credit Suisse said it was cooperating with authorities after its offices in London, Paris and Amsterdam were contacted by officials "concerning client tax matters."
The Netherland's office for financial crimes prosecution (FIOD) said the coordinated raids began on Thursday in the Netherlands, Britain, Germany, France and Australia after receiving a tip-off about 55,000 suspect accounts of a Swiss bank. It did not identify the bank.
The U.K.'s HM Revenue and Customs did not identify the bank either in a Friday statement, saying it had started a "phase one" investigation into a "global financial institution" focused on senior employees and a number of its customers.
"The international reach of this investigation sends a clear message that there is no hiding place for those seeking to evade tax," HMRC said.
Credit Suisse pleaded guilty to similar charges in 2014 in the U.S. It paid $2.6 billion for an "extensive and wide-ranging conspiracy" to help U.S. clients evade tax.
But the raids look set to clause an international incident with the Swiss attorney general's office saying it was "astonished at the way this operation has been organised with the deliberate exclusion of Switzerland. The normal customs and rules of international cooperation and legal assistance procedures have apparently not been observed. The federal public prosecutor expects a written explanation from the relevant leading Dutch authorities, and is considering further steps."