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Società di persone: litisconsorzio holds even for IVA

Without every partner joined, the judgment is void: the Corte di cassazione remits the 2005 notices to first instance and confirms the rule even for IVA.

Even where the act assesses IVA (Italian VAT), all the partners of a società di persone (Italian partnership) must be parties to the same proceedings: if one is left out, the judgment is void, the defect may be raised by the court of its own motion at any stage and instance, and the merits are not examined. So held the Corte di cassazione (Italian Supreme Court), Fifth Civil Division (tax), in ordinanza (order) 16 September 2026, no. 25439 (ECLI:IT:CASS:2026:25439CIV), decided in chambers on 11 September 2026.

The facts

A s.a.s. (Italian limited partnership) and its general partner brought three separate challenges against two avvisi di accertamento (notices of assessment) — additional IVA taxable base for the partnership and additional IRPEF income from participation for the partner, year 2005 — and against the penalty for failure to reply to a questionnaire. At first instance the challenges were allowed by three judgments; the appeals having been joined, the Corte di giustizia tributaria di secondo grado (regional tax court) of Puglia (judgment no. 2529/28/2022, filed on 30 September 2022) allowed the tax office’s appeal on the penalty head alone and upheld the IVA deduction on the registers produced in the proceedings by the partnership, which was later declared bankrupt. As to time limits, the Court confirms that the appeal to the Corte di cassazione, served on 18 May 2023 against the judgment filed on 30 September 2022, was brought in time, by reason of the eleven-month suspension of the time limits for challenging decisions provided for by art. 1, comma 199, della legge 29 dicembre 2022, n. 197.

The rule of law

The Court does not examine the grounds: of its own motion it raises a question that comes first. Where the adjustment of the returns of the partnership and of the partners stems from a single, unitary assessment, litisconsorzio necessario (mandatory joinder of parties) applies and the court must order that the other parties be joined (art. 14 del d.lgs. 31 dicembre 1992, n. 546); failing that, the proceedings are affected by absolute nullity, which may be raised at any stage and instance (Cass. n. 16730/2018; n. 7278/2020).

On IVA the Court confirms settled case law: taken on its own, IVA raises no question of litisconsorzio; but where a single act assesses other taxes as well — IRAP, for instance — on common elements, the IVA aspect too is not removed from the simultaneus processus (Cass. n. 6303/2018; n. 21340/2015; n. 10550/2025). It does not appear from the text of the ordinanza that the single act addressed to the partnership assessed IRAP as well; in any event, the Court anchors the requirement — “all the more so” — to the “personal” notice by which the additional income from participation was attributed to the partner by transparency for IRPEF purposes (Cass., sez. un., n. 14815/2008).

A further partner, himself the addressee of a “personal” notice, was not a party to the proceedings on the merits: the Court declares the whole of the proceedings on the notices void and remits the file to first instance. The penalty head stands, having been imposed on the partnership alone and therefore severable; no internal res judicata has formed, because the defect concerns the joinder of the parties (Cass., sez. un., n. 24172/2025).

What remains to be decided

Twenty-one years on, the merits are still to be examined: the unusability of the documents not produced in reply to the questionnaire, and the deduction based on the IVA registers alone, have not been assessed. A sound position on the merits is no protection against incomplete joinder.

In practice

Before filing. The adviser reconstructs the membership of the partnership for the year assessed (visura storica, the historical registry extract, and libro soci, the register of partners) and identifies the addressees of the “personal” notice: income is attributed in proportion to the share in profits (art. 5 del TUIR). Where insolvency proceedings are pending, check who must be called into the proceedings.

Within the time limit for challenging. Counsel files a single cumulative challenge for the partnership and the partners — including those who have withdrawn and those who have joined — or separate challenges, at once applying for them to be joined and for the other parties to be brought in (art. 14, comma 2, del d.lgs. 546/1992).

On appeal. If the parties were not joined at first instance, counsel applies for remittal (art. 59, comma 1, lettera b), del d.lgs. 546/1992). The point may also be raised for the first time before the Corte di cassazione.

After remittal. The party with an interest in doing so resumes the proceedings against all the parties personally within the mandatory time limit of six months from publication of the decision; failing that, the whole of the proceedings is extinguished (art. 63, commi 1 e 2, del d.lgs. 546/1992). The partners left out will then be called into the proceedings under the first-instance court’s order that the other parties be joined (art. 14, comma 2).

On the merits. The documents not produced in reply to the questionnaire are to be filed with the document instituting the proceedings at first instance, with a declaration that the failure to produce them was due to a cause beyond the party’s control (art. 32, commi 4 e 5, del d.P.R. 600/1973).

The provisions cited remain in force: the testo unico della giustizia tributaria (consolidated act on tax justice, d.lgs. 175/2024) applies from 1 January 2027, a date deferred by art. 4, comma 3, del d.l. 200/2025, converted by l. 27 febbraio 2026, n. 26; from the same date the testo unico adempimenti e accertamento (d.lgs. 141/2026) and the new testo unico delle imposte sui redditi (d.lgs. 117/2026), which absorbs art. 5 of the current TUIR, also apply.

Frequently asked questions

The notice was served only on the partnership and on one partner: must I bring the others into the proceedings?
Yes. Litisconsorzio follows from the unitary nature of the assessment, not from the notices actually served: the court must order that the other parties be joined, failing which the judgment is void.

Does the requirement apply to IVA as well?
IVA on its own does not impose it: it arises where a single act assesses IVA together with other taxes — IRAP, for instance — on common elements. In the case decided the Court added to this, “all the more so”, the unitary nature of the assessment as between the partnership and the partner.

Sources

Corte di cassazione, Fifth Civil Division, order of 16 September 2026, no. 25439 (ECLI:IT:CASS:2026:25439CIV), chamber sitting of 11 September 2026, President Perrino, Judge Rapporteur D’Alessandro; full text consulted on Italgiure, the Corte di cassazione judgment database.

Articles 14, 59(1)(b) and 63 of Legislative Decree no. 546 of 31 December 1992, text in force as at 23 September 2026.

Article 32(4) and (5) of Presidential Decree no. 600 of 29 September 1973, text in force as at 23 September 2026.

Article 5 of the TUIR, the consolidated income tax act approved by Presidential Decree no. 917 of 22 December 1986.

Article 4(3) of Decree-Law no. 200 of 31 December 2025, converted, with amendments, by Law no. 26 of 27 February 2026, replacing, in Article 131(1) of the testo unico on tax justice approved by Legislative Decree no. 175 of 14 November 2024, the words “1 January 2026” with “1 January 2027”.