Case C-340/15: Judgment of the Court (Third Chamber) of 12 October 2016 (request for a preliminary ruling from the Bundesfinanzgericht — Austria) — Christine Nigl and Others v Finanzamt Waldviertel ((Reference for a preliminary ruling — Taxation — Value added tax — Sixth Directive 77/388/EEC — Article 4(1) and (4) — Directive 2006/112/EC — Articles 9 and 11 — Concept of ‘taxable person’ — Civil-law partnerships selling their products under a common trade mark and through a limited company — Concept of ‘independent undertaking’ — Refusal of the status of taxable person — Retroactivity — Sixth Directive 77/388 — Article 25 — Directive 2006/112 — Articles 272 and 296 — Flat-rate scheme for farmers — Exclusion from the flat-rate scheme — Retroactivity)