smartsteuer is an online application for preparing German income tax returns, offered by smartsteuer GmbH in Hannover. Users answer guided questions, see the expected refund calculated live, and have the return checked before submitting it electronically to the tax office. It serves employees, self-employed people, students and pensioners, and the company also offers a product for the German property tax (Grundsteuer). Self-employed users can transfer income, expenses and receipts through an interface to Lexware Office.
smartsteuer GmbH is based in Hannover, Germany, and according to its imprint belongs, as a majority holding, to Haufe-Lexware GmbH & Co. KG, part of the Haufe Group, which has its seat in Freiburg. Both are German, so no foreign parent applies. The privacy notice says data is processed in a high-security data centre but does not name its location, so ask the vendor to confirm it. No self-hosted variant exists; the service is online only.