The " Netflix tax " is very specific. It relates to intangible services sold by companies that are not based in Australia and do not currently pay GST on the services it provides. Intangible services are principly digital services that do not have a physical presence, such as overseas streaming of movies and TV shows etc. ( hence the name )

Ebay is caught up in this as its main Company is registered in an overseas tax haven  ( Switzeland from memory ) Ebay provides the digital platform that Australian sellers sell on. ie. Digital internet based auctions and BIN listings.

People who sell on ebay use these digital services and so pay 10% extra in GST tax to the ATO on the ebay service charges only. Ebay collects and remits this money, the seller does nothing extra except pay the extra small fee, added to their commission and listing fees.

 The Netflix tax only relates to ebays fees and has nothing really to do with the privately owned items you sell. You dont have to do anything outside the norm and the tax generally adds up to around 1 -1.5% of your total item selling price including postage, so not a biggy for private sellers.