Case C-127/18: Judgment of the Court (First Chamber) of 8 May 2019 (request for a preliminary ruling from the Nejvyšší správní soud — Czech Republic) — A-PACK CZ s. r. o. v Odvolací finanční ředitelství (Reference for a preliminary ruling — Common system of value added tax (VAT) — Directive 2006/112/EC — Articles 90 and 273 — Total or partial non-payment, by the debtor, of a sum due to the taxable person in respect of a transaction subject to VAT — Taxable amount — Reduction — Principles of fiscal neutrality andproportionality)