A German who promises to pay another person’s debt must give that promise in writing. Section 766 of the Civil Code says: Zur Gültigkeit des Bürgschaftsvertrags ist schriftliche Erteilung der Bürgschaftserklärung erforderlich. For the guarantee to be valid, the guarantor must give his declaration in writing. An e-mail is not enough. The same section excludes the electronic form. In a judgment of 17 February 2000, the Federal Court of Justice described the purpose. The form requirement soll den Bürgen warnen und vor nicht ausreichend überlegten Erklärungen sichern. It is meant to warn the guarantor and to protect him from a declaration he has not thought through. Merchants are the exception. Under Section 350 of the Commercial Code, a guarantee that is part of their business is valid without the written form.