All documents other than annexes filed after filing the European patent application must be signed by the person responsible. The principles of Art. 133 are that only the applicant or his representative may act in the European patent grant procedure. Documents filed after filing the European patent application may therefore be effectively signed only by these persons.

Documents such as the priority document or the translation thereof must be accompanied by a separate letter or at least bear a note on the document itself that it is addressed to the EPO, duly signed by a person authorised to act before the EPO. This also applies, for example, to the designation of inventor if this has been signed by an applicant with neither residence nor principal place of business in one of the Contracting States to the EPC. As regards the authorisation, see IX, 1.5. The signature of the entitled person confirming performance of a written act of procedure helps to clarify the state of the proceedings. It shows whether the act of procedure has been validly performed, and also prevents circumvention of the provisions relating to representation. Form 1038 (Letter accompanying subsequently filed items) may also be used as a separate letter. A separate form must be used for each file (see the Notice from the EPO, OJ 1-2/1991, 64). In the case of electronic filing, several documents for a file can be attached on a single Form 1038E.

If the signature is omitted on a document not falling within the meaning of IX, 3.2, the EPO must invite the party concerned to sign within a fixed time limit. This also applies if the document in question bears the signature of an unentitled person (e.g. the secretary of an authorised representative), a deficiency which for the purposes of the time limits under way is treated as equivalent to omission of the signature of an entitled person. If signed in due time, the document retains its original date of receipt; otherwise it is deemed not to have been received. Likewise, documents filed electronically must be signed by an entitled person, although they may be transmitted using a smart card issued to another person. See also 3.2 below.