Good article here : https://www.moneyland.ch/en/stock-market-profits-tax-free
I would directly read the circulaire from the ESTV/AFC. It is a bit longer but you have the official informations (which are the same of this article but longer with references to federal court judgements etc.).
Edit : Circulaire No 36 (apparently it is only 8 pages, I thought it was longer). According to the file name, looks like I dowlnoaded it 3 times
Bought 50,000 CHF worth of stock by mistake which I sold immediately afterwards with a total loss of 35 CHF.
I wanted to sell 50,000 originally, accidentally bought 50.000 and ended up selling both the original and accidentally bough 50,000 CHF for a total sale of 100,000 CHF.
Do you think the tax office will realize that I made a mistake and not designate me as a professional investor despite not holding for 6 months ?
No personal direct experience like that, but based on other experience made (let’s say “worse”, selling for a profit after a month etc) I think that they definitely won’t classify you pro due to a trade like that.
I find there is generally way too much nervosity by “simple investors” on this forum about being classified a pro investor. If you have a full-time day-job you’re 99% safe for a start IMO, then u would need huge profits, fancy stuff day trading options, etc.