IP Cases & Articles

Rule 56a EPC: correction of erroneously filed parts of a patent application

European patent law currently provides applicants with a limited window following the filing date of a patent application to file further parts of the description or drawings that were missing in the documents originally filed. Specifically, Rule 56 EPC allows applicants to file missing parts of the description of drawings within two months of the filing date or from a notification from the European Patent Office (EPO) that missing parts have been identified. If this provision is used, the filing date of the application is re-dated to the date the missing parts are received at the EPO, unless these parts were completely contained in an earlier application from which the application claims priority.

There is no provision at present, however, to correct the filing of erroneously filed parts, that is, parts of the application that were never intended to be filed but will, however, be published if the application is not withdrawn. Thus, in the situation where erroneously filed parts of the description or drawings disclose information that should not be made public for commercial reasons, the only solution under the law as it stands is to simply withdraw the application containing the erroneous subject-matter and file another application. In this unfortunate situation, the filing fee already paid for the application containing the erroneously filed parts would be lost, and, more seriously, having to refile the application at a later date could result in the priority claim being lost due to filing outside the priority year.

New Rule 56a EPC

This is set to change from November 2022 with the introduction of new Rule 56a EPC. This new rule will bring the EPC into line with an equivalent provision introduced into the PCT in July 2020, Rule 20.5bis PCT. These provisions of the EPC and PCT, in contrast to previous “missing parts” provisions, explicitly provide for the exchange of correct parts of the description or drawings with the erroneously filed parts of the description or drawings in a patent application after filing.

From November 2022, in addition to being able to introduce missing parts of the description and drawings in the two-month window after filing or notification from the EPO, it will also be possible for applicants to correct erroneously filed parts of the application, which will be deemed not to have been filed under the new provisions and hence not be published. The EPO will, from November 2022, also fully apply Rule 20.5bis PCT when acting as receiving office, thus enabling applicants to make use of the analogous procedure under the PCT for international applications filed at the EPO.

The procedural aspects of new Rule 56a EPC will essentially mirror those of current Rule 56 EPC. If the erroneous parts of the description or drawings are corrected after the filing date, the application will be re-dated to the date on which the correct parts are received, unless those parts are completely contained in an earlier application from which the application containing erroneously filed parts claims priority.

It is important to note that a significant difference between new Rule 56a EPC and current Rule 56 EPC is that in order to retain the filing date due to the correct parts being “completely contained” in the earlier application, priority must have been claimed from this earlier application on the filing date of the application. This contrasts with the situation for current Rule 56 EPC, where priority of an earlier application may be claimed after filing in order to introduce missing parts completely contained in that earlier application. Rule 56a EPC will thus be less flexible for applicants, and shows the importance of declaring priority of any relevant earlier applications on the filing date.


Of course, it is good practice to avoid reliance on such provisions in the first place, and indeed the use of such provisions is rare in practice. However, it would be naïve to assume that filing errors never occur, and hence it is important to be aware of how such errors can be corrected. In the event that errors are identified with a particular application, it is also best practice to file a corrected application as soon as possible, without paying fees, as an additional safety measure in case there is any issue with the use of the provisions discussed above.

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