You will need proof that the goods have been exported.
Problem is that only a few form of proof are accepted: https://www.ezv.admin.ch/ezv/en/home...portation.html
Which means you have to do an e-dec export for each shipment
https://www.ezv.admin.ch/ezv/en/home...ec-export.html
and fill in a CN23 instead the simpler green CN22 if you use regular post.
Wow, what a bureaucrazy [sic!]. It is much simpler for EU businesses to sent goods VAT free out of the EU There the shipment tracking is good enough for goods up to
Yeah, that's a PITA but things are much better today: post has APIs for this and it can be integrated into store / order management system for completely automated processing.
I hope threadstarter has such system because relying on eBay to manage your sales is very dangerous thing. The bastards can suddenly decide that you are not a good customer and start to terrorize you by removing listings *AND* templates, blocking account etc. All it takes is a competitor that decides to report your listings and boom.... I've been through all of that and we shed blood tears before we created our own system to manage stock / orders / eBay.