B2G + B2B + B2C. All VAT-registered persons established in Italy, no turnover threshold since 1 Jan 2024 (includes forfettari). Non-established/non-resident businesses are NOT obliged to issue via SdI (they may opt in); their transactions are captured through the resident counterparty's cross-border TD reporting. B2C healthcare services are excluded by law.
Two traps. (1) The EU derogation runs out on 31 Dec 2027 — Italy must renew it or fold SdI into the ViDA framework; anyone writing a multi-year roadmap should not assume SdI is permanent in its current form. (2) FatturaPA is NOT natively EN 16931 — it is a national XML with an Italian CIUS, so cross-border ViDA alignment will require change. Also note the technical specs are a moving target (v1.9 from 1 Apr 2025 added TD29/RF20; v1.9.1 from 15 May 2026) — a 'live since 2019' framing hides real annual integration work.
4 of 5 are primary sources. Mandate dates move — treat this page as a starting point and confirm against the primary source before committing a plan.
A page is a starting point. A scoped analysis gives you the specification, the mapping and the effort — in weeks, not quarters.