As I see here , there is no obligation with AHV/AVS. Also I will declare this additional income in my tax form. What I am not sure about, is that if I have to register an individual company for this second job or not needed?
I am fully employed in a company (100%) and as a secondary occupation during one or two week-ends I am intending to do some freelance job for a friend. The annual earnings will be less than 2300 CHF for the second job.
When I was working at a startup we hired a graphic designer for one off task, a couple of weeks. I asked once how freelancers are doing business here in Switzerland. The answer was along the line: "I don't have a company, just declare all the invoices on my tax return, but I am Swiss, for you requirements may be different."