Tax authorities in the canton of Zurich are demanding 1.5 million francs ($1.6 million, €1.2 million) from the family of an Austrian man who committed suicide after he was arrested in September 2010 for stealing and selling the data to authorities in the German state of North Rhine-Westphalia, the ATS news agency reported.
The 42-year-old Credit Suisse employee reportedly received 2.5 million francs for the stolen data, which led German authorities to raid branches of the Swiss bank in 13 German cities.
According to ATS, Swiss authorities had blocked the heirs' access to his entire estate in anticipation of the tax payment.
The tax cheat data incident caused a major row between Germany and Switzerland, which reacted angrily, saying the data were stolen in violation of its banking secrecy laws.
As much as €180 billion in German assets are hidden in Switzerland, according to unconfirmed German media reports.
A tax deal between the two countries, aimed at ending such disputes, is to take effect in January 2013 but still needs to be ratified by both houses of the German parliament.