Personally, I think eBay's choice to collect it this way is wrong - they are the ones with the obligation to collect and remit the tax, and the person or entitiy who has that responsibility is the one who needs to have that on their records (not to mention they're the ones who should bear any costs of that collection). It's not the same as an Aussie seller collecting GST and having to include it in their price, because they obviously have all of those aforementioned responsibilities.
I don't sell internationally on eBay, but I do elsewhere and that marketplace also collects sales tax on orders from buyers in NZ and applicable US states - I don't receive the money, I don't get to use the money in any way, and I don't have the responsibility of handing it over to anyone, so I don't count it as an income / expense at all - it's less complicated though, because while the total paid by the buyer is shown on my records, the taxes are never paid to me at all, it's a separate transaction and the funds go directly to Etsy - that's how eBay used to do it, in a way, except because they're not set up to be paid directly yet, the funds went to an eBay-controlled PayPal account, now they're being paid to the seller, and the seller is paying fees on the amount, so it is forcing them to receive income and have expenses on that income - because of that, I'd probably recommend talking to an accountant on the best way to reflect it on your books, JMHO.
I kinda hope that once their managed payments system is implemented, they go back to receiving the taxes directly rather than see it as an opportunity to make money from their tax obligations.
