Banker in Paris. Established as a merchant in Amsterdam (c. 1768). Went to Paris (1777). With Jean Girardot de Marigny, took over the former Necker family bank, under the name of Girardot, Haller & Cie. (August 1777). The firm unsuccessfully attempted to become the primary bankers to the American Commissioners. Used his many business contacts in England, Holland, and France to speculate extensively on the war. A longtime associate of Thomas Walpole, he arranged a clandestine transfer in English funds from Edward Bancroft to Walpole (August 1778).

Born in Bern. Son of the well-known Swiss intellectual and poet, Albrecht von Haller. Married in March 1777 to Gerardine Van der Dussen, member of a prominent Dutch family.