Attention you are declaring that your entity is not subject to an NACE code
Una pubblica amministrazione o un ente dotato di personalità giuridica non è obbligato a possedere un codice ATECO, a meno che non svolga anche attività di natura economica o commerciale assimilabili a quelle di un'impresa o di un libero professionista.
Le pubbliche amministrazioni (ad esempio, Comuni, Regioni, Ministeri, ecc.) generalmente non svolgono attività economiche, ma funzioni pubbliche e istituzionali. Per questo motivo, non rientrano nei soggetti obbligati ad avere un codice ATECO.
Eccezioni:
Un ente pubblico o una pubblica amministrazione può essere tenuto ad avere un codice ATECO solo se:
Svolge attività economiche in aggiunta alle proprie funzioni istituzionali. Ad esempio, gestione di un'attività commerciale come una fiera o un impianto sportivo aperto al pubblico.
Ha una componente separata (come un'azienda speciale o un servizio economico) che opera con una struttura simile a quella di un'impresa.
In questi casi, il codice ATECO serve per identificare l'attività specifica ai fini delle dichiarazioni fiscali o per l'iscrizione in specifici registri (come quello della Camera di Commercio).

Here is a list of the main public and institutional functions that, as such, do not require an ATECO code, as they do not engage in economic or commercial activities. These functions are typically performed by public entities or entities with exclusively institutional purposes:
1. General State Administration Government and constitutional bodies. Ministries (e.g., Ministry of the Interior, Ministry of Economy and Finance). Prefectures. National Defense (Armed Forces, Carabinieri).
2. Local Administrations Municipalities, Provinces, and Metropolitan Cities. Regions and their legislative assemblies. Territorial offices with administrative functions (such as registry offices, civil status).
3. Security and Public Order State Police and security forces (Carabinieri, Guardia di Finanza, Penitentiary Police). Civil Protection. Fire Brigades (when not engaged in related economic activities).
4. Justice Ordinary and administrative courts. Judicial offices (Prosecutor's offices, Courts of Appeal). Justice of the Peace offices.
5. Education and public instruction Public schools of all levels (preschool, primary, secondary). State universities. Public and academic research institutes.
6. Public healthcare Public hospitals and local health authorities (limited to non-economic institutional activities). State clinics and healthcare facilities. Health prevention (vaccinations, pandemic control).
7. Welfare and social assistance Social services for family, child, and elderly care (not economically significant). Public employment centers. Pension management and social security contributions (INPS, INAIL, etc.).
8. Culture and historical-artistic heritage Superintendencies for cultural heritage. State and municipal museums that do not engage in commercial activities (for-profit ticketing). Public libraries and archives.
9. Environment and Territory Management of protected areas (national and regional parks) without commercial purposes. River basin authorities and water resource management (non-economic). Urban and regional planning offices.
10. Transport and Infrastructure Management of public roads (roads, bridges, railways) not related to economic activities. Air traffic control (if part of state civil aviation). Free or subsidized public transport services (not for profit).
11. International Relations Embassies and Consulates. Italian representations at international organizations (UN, EU, NATO, etc.).
12. Defense of rights and protection of citizens Ombudsman. Data Protection Authority. Authority for the rights of minors and the elderly.
These functions are strictly linked to institutional competences and, unless they carry out ancillary economic activities, do not require an ATECO code.

Are you sure that your entity is not subject to an ATECO/NACE code?