Do I need both German VAT and OSS?

It depends on where you sell. Storing stock in Germany requires a German VAT registration from the first euro. OSS (the EU One-Stop-Shop) is a separate return for sales to consumers in other EU countries, and whether you need it depends on your sales channel. If your company is established outside the EU and sells to consumers only through a marketplace such as Amazon, the marketplace counts as the seller of those sales for VAT (the deemed supplier rule, § 3 (3a) of the German VAT Act, UStG), so those sales need no OSS. OSS matters for sales through your own webshop. The €10,000 EU-wide threshold is only available to sellers established inside the EU, so for a seller established outside the EU OSS applies from the first such sale; an EU-established seller needs OSS once its EU-wide sales to consumers pass €10,000 a year, and files it in its home country, not Germany. Tell us your sales channels and we confirm which of the two you need before you book.