What time limits apply to filing new documents or requests during opposition proceedings?
The Paris Court of Appeal ruled on 4 July 2025 on an appeal against a decision of the French National Institute of Industrial Property (INPI) in an opposition to a French patent. The Court of Appeal’s decision confirms the strictness of the admissibility rules applicable, both during the opposition proceedings before the INPI and on appeal, as regards requests, arguments and documents filed in the course of the proceedings.
We will publish our analysis in two parts: a first focused on the opposition proceedings before the INPI, then a second on the appeal before the Court of Appeal.
In this article, we briefly present the case at issue, then address the first part. The second part will be dealt with in a second article to be published.
1. The Linxens v. Thales case
On 9 July 2021, the INPI granted the patent “Smart card and method of manufacturing a smart card” to Linxens Holding (hereinafter “Linxens”). This patent was challenged by Thales:
- on 8 April 2022, Thales filed opposition proceedings against this patent,
- on 13 September 2023, the Director General of the INPI revoked it in its entirety,
- on 11 October 2023, Linxens lodged an appeal against that decision,
- by a judgment of 4 July 2025, the Paris Court of Appeal upheld the INPI’s decision: the patent is revoked.
2. Linxens’ arguments against the INPI’s decision
In its appeal before the Court of Appeal, Linxens reproached the INPI for having disregarded the principle of adversarial proceedings during the opposition. It relied on three arguments:
- Thales had made a late filing of observations and a prior-art document (D15) on the last day of the written phase, without any possibility to respond;
- the INPI had rejected an auxiliary request for amendment, filed during the oral phase, on the ground of late filing;
- the INPI raised of its own motion an objection of intermediate generalisation, without having first invited the parties’ observations.
We will analyse in detail, in the Court of Appeal’s decision, the first two points, which we consider the most important. But first, let us recall the different phases of an opposition before the INPI.
3. The phases of an opposition before the INPI
Opposition proceedings before the INPI are structured, in accordance with Article R. 613-44-6 of the French Intellectual Property Code, into four successive phases:
- An information phase;
- A development phase;
- A written phase;
- An oral phase, during which the parties may still present observations and requests.
In these proceedings, the written phase and the oral phase are not completely compartmentalised. The end of the written phase does not mark the definitive closure of the proceedings: the patent proprietor retains the possibility, in theory, during the oral phase, to submit further observations or even to file new requests.
This flexibility distinguishes the INPI opposition procedure from the civil procedure regime. In civil procedure, the closure of the investigation entails a genuine locking of exchanges.
4. The Court of Appeal’s decision
Is filing a new document just before the close of the written phase considered late?
In its appeal before the Court of Appeal, Linxens argued that Thales had made, during the opposition proceedings, a late filing of a prior-art document. Since this filing took place on the last day of the written phase (only one month before the oral phase), Linxens contended that it did not allow it to analyse this document in depth or to prepare observations in reply. The Court nevertheless noted that Linxens had not shown that it was unable effectively to respond to these new items, nor to debate them during the oral phase of 16 May 2023.
Accordingly, the Court of Appeal rejected this ground. The Court considered that filing a document on the last day of the written phase does not in itself amount to a breach of the adversarial principle, provided that the opposing party had a concrete opportunity to be heard before the close of the debate.
In other words, the closing of the written phase before the INPI does not deprive the parties of their right to be heard until the end of the proceedings.
From a practical standpoint, one can imagine that Linxens could have requested a postponement of the oral phase, citing the lack of time to examine the newly produced document D15.
Such a step, had it been refused by the INPI, could have strengthened the credibility of its argument that it had not had an effective opportunity to respond to the new documents at the hearing of 16 May 2023.
In that event, the grievance based on a breach of the adversarial principle would have been more persuasive before the Court.
Is an auxiliary request filed during the oral phase to be regarded as a late request?
During the oral phase, Linxens submitted a second auxiliary request for amendment; the INPI refused to admit it on the ground of late filing.
The Court of Appeal upheld this assessment: the request must be considered late, and its refusal is justified for reasons of proper administration of the proceedings.
According to the judgment of 29 May 2024 (BMW, opponent v. Michelin, patentee), the criterion for admissibility of new requests submitted during the oral phase is that the adversarial principle can be respected, in accordance with the provisions of the Intellectual Property Code.
In Linxens v. Thales, the Court noted that:
- Linxens’ request was complex, comprising four independent claims, whereas the original patent contained only two;
- and that it was filed in the course of the oral proceedings.
Thus, the Court considered that this request, being complex and late, did not allow an effective adversarial debate. The INPI’s refusal is therefore confirmed, in the name of proper administration of the proceedings.
A strict assessment of the criteria
To justify the inadmissibility of the new request, the Court of Appeal did not rely on another possible argument: Linxens could have filed its request earlier. By contrast, in proceedings before the EPO, it is common for one of the arguments against a late filing to be that the item could have been provided earlier, in particular within the prescribed time limits. The EPO considers, for example, that the objection was already known, but that the party did not submit this item, without any apparent reason.
Moreover, it is not uncommon before the EPO for observations or requests to be filed after the date set under Rule 116(1) EPC (European Patent Convention), but before the oral proceedings. Their admissibility then depends on the circumstances of the case and on the opportunity afforded to the opposing party to prepare.
If Linxens had filed this new request before the oral proceedings, would the assessment of its admissibility have been different?
A priori, the INPI’s practice appears less flexible than that of the EPO.
One may cite in particular the decision of the opposition division, INPI OPP22-0015 of 9 February 2024 (commented on our site here), according to which such a request is in principle inadmissible, save in particular circumstances. In that case, these requests were admitted because the opponent indicated that it had had time to take note of them.
A procedural advantage for the opponent?
We have seen, on the one hand, that the filing by the opponent of a prior-art document on the last day of the written phase may be admitted, but, on the other hand, that an amendment request filed by the proprietor between the end of the written phase and the start of the oral phase may not be admitted absent the opponent’s agreement.
Accordingly, one may wonder whether such a combination does not create a procedural imbalance: an opponent could file a new document at the very end of the written phase, while the proprietor, if it wishes to respond with a new request after that written phase, even before the oral phase, would risk being faced with a refusal on the ground of a late request. This asymmetry may appear unfavourable to the patent proprietor.
One could also consider that the existence of a link between the new document submitted by the opponent and the proprietor’s new request could influence the assessment of the admissibility of that request. In Linxens v. Thales, the Court does not specify whether such a link is established. The question therefore remains open.
By Manqi ZHU, 10 March 2026
Image credit: Riccardo Fraccarollo, Pexels