About 7,000 mostly German customers of the Swiss bank are being targeted. They are thought to have invested in what the bank called an insurance plan, but was actually a tax-free bank account, the Handelsblatt said.
"We are aware that German tax authorities are looking into some of our clients," a spokesman for the bank told AFP, confirming the report.
"We are talking about customers living in Germany but with accounts with Credit Suisse in Switzerland," the spokesman added.
"There is no investigation against the bank," he added.
While the average amount invested by customers was around €500,000, some had up to €12 million stashed away, tax-free, with the bank's subsidiary Credit Suisse Life, which is based in Bermuda.
Billions of euros of taxes were avoided in this way, the newspaper said.
"We have advised clients to consult tax experts to check their tax situations and, if necessary, to make themselves available to authorities," Credit Suisse spokesman Marc Dosch was quoted as saying.
He added that the bank offered only above-board services, and that customers sign a release agreeing to take taxation issues into their own hands.