Hi there,
Although bank customer secrecy for residents of Switzerland is stipulated by Swiss law, a number of Swiss banks include special clauses in their customer agreements which relieve them - either partially or in full - from their privacy obligations.
In addition to the WIR Bank, Postfinance includes such clauses in its customer agreements, as do a handful of specialized banks.
Large banks with international operations are more easily affected by foreign regulations than banks which operate in Switzerland only. Smaller banks are less likely to be targeted by foreign tax authorities looking to steal customer information. This can make regional or cantonal banks a good choice for privacy-minded customers.
In any case, it is important to carefully read the terms and conditions of a banking agreement before you sign up.
Best regards from Moneyguru
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Swiss banking secrecy explained