I have implemented In-app billing in my application, but have limited the in-app purchase function to a few countries/currencies, since I\'m note sure what my responsibilite
In case of Japan and GooglePlay, you have to do the whole VAT procedure on your own if your income reaches a threshold of 10 million Yen (about 95 kUSD) per year, otherwise no action from your side required. If you make that much money you could probably pay a tax professional to deal with this.
Source: National Tax Agency JAPAN
No.6 Taxable Person Business which falls under either of the following categories is a “Taxable Person” who is required to file the final return.
(1) Businesses which had a taxable sales amounting to more than 10million yen during the Base Period (See following Figure A), ...