We are an unmarried couple living and working in Zurich, each of us holds a B permit and is taxed directly at source. How should we report dividend income from a joint account at Interactive Brokers (or any other joint income, for that matter)? My naive approach would be to split the income at 50%, but I could not find any valid source.
If you are not married, there is no such thing as “joint ownership” for you in CH under the swiss laws. You both have separate estates and own a certain percentage of assets in that “joint” account. Presumably according to how much each of you contributed. Or maybe the agreement between the two of you how assets and profits are to be split. Declare that percentage, obviously.
For unmarried couple, a judge would consider them a société simple by analogy. That means that whitout any aggreement, profits are to be split equally, irrespective of their contributions (art. 533 al. 1 CO).