Bank secrecy rests on the contractual commitment made by the banker to keep silent about his or her client's personal situation. The contractual relationship between the client and the bank generates banker duty of confidence - a natural consequence of the client's trust.

The legal basis of the banker's duty has a complementary source in the fact that the banker often serves as proxy, while the client is the "master of the secret", so to speak. By breaking the duty of secrecy, the banker violates his or her obligation. The banker is held by Articles 97 et seq. of the Labor Code to compensate for the damages incurred. It is on this basis that the client can take civil action for damages against a bank for violating its duty of secrecy.

Article 98 al. 2 of the Swiss Labor Code Anyone who contravenes an obligation to abstain from action owes damages by the very fact of contravention