Ive had my car for over 6 months and with the free trade agreement I can bring it to Switzerland tax-free, although I wonder do I still need to do the CO2-test and pay if it is over the limit? Or is it only applied to importers? Ive tried to reach Astra but no success to receive an answer.
Which free trade agreement? I am not aware of any free trade agreement which concerns tax (apart from the one with Liechtenstein, and the one with Germany regarding Büsingen).
For CO2 they look at the WLPT or NEDC data in the cars COC.
Regarding 6 month limit:
https://www.bfe.admin.ch/bfe/en/home…/cars/faq.html
The CO2 import limit only applies to commercial importers of new cars, it does not concern you.
For tax and duty free import as part of a household move (which is just a gesture from Switzerland and not based on any treaty) the car must have been used (not necessarily owned) by the importing person for at least 6 months. This also means that the car must have been registered for at least for 6 months.
The CO2 tax also affects private importers, not just commercial ones. The tax is only levied on new car which have not been registered abroad for 6 months or more. It follows that in case of a tax and duty free import as part of a household move, this requirement is fulfilled. In case the car was used for less than 6 month the actual import can be deferred for up to 24 months, and thus also no CO2 tax has to be paid.