VAT Registration in Austria
In Austria, VAT is called USt (Umsatzsteuer). You register with the Finanzamt (tax office) to obtain a UID-Nummer (VAT identification number).
Kleinunternehmerregelung (Small Business Exemption)
Austria offers a VAT exemption for businesses with annual turnover below €55,000. Under this scheme, you don't charge VAT but also cannot reclaim input VAT.
Include on invoices: "Umsatzsteuerbefreit gemäß § 6 Abs. 1 Z 27 UStG."