"Self-employed individuals operate externally under their own company name. They possess their own infrastructure and issue invoices in their own name, bear the collection risk and, under certain circumstances, pay VAT. They bear their own economic risk. They decide themselves how they are organized, how they work and whether to pass on work to third parties. Furthermore, self-employed individuals always work for several clients. An agent is also not deemed to be self-employed if he or she performs his or her work in the business premises of a client and works exclusively for this client."
Source: AHV Federal Office for Social Insurance