Does ST.26 apply to divisional applications?

Yes. Under the EPC, a divisional application is an independent application subject to the procedural requirements applicable on the date of its submission. Therefore, any divisional application submitted on or after 1 July 2022 and disclosing nucleotide or amino acid sequences (four or more amino acids or ten or more nucleotides) must include a sequence listing complying with WIPO Standard ST.26.  

Where the parent application contains a sequence listing complying with WIPO Standard ST.25, that listing must be converted into one complying with WIPO Standard ST.26. 

An earlier (parent) application's sequence listing that complies with earlier standards (e.g. WIPO Standard ST.25) may not be added to the file of the divisional application "for search only". In such cases, the applicant must include a sequence listing that complies with WIPO Standard ST.26 in their divisional application.

For more details, see OJ EPO 2021, A97.