Correction of description, claims and drawings
Where the mistake is in the description, claims or drawings, both the error and the correction must be such that it is immediately evident:
that an error has occurred; and
what the correction should be.
Regarding (i), the incorrect information must be objectively recognisable for a skilled person, using common general knowledge, from the originally-filed application documents (description, claims and drawings) taken by themselves.
Regarding (ii), the correction should needs to be within the limits of what a skilled person would derive directly and unambiguously, using common general knowledge, and seen objectively and relative to the date of filing, from the originally-filed application documents.
In other words, the requirements of Art. 123(2) apply mutatis mutandis.
Evidence of what was common general knowledge on the date of filing may be furnished in any suitable form.
The priority documents cannot be used for the purposes mentioned under (i) and (ii) above (see G 3/89 and G 11/91).
Correction under Rule 139, second sentence, is of a strictly declaratory nature and establishes what a skilled person, using common general knowledge, would derive on the date of filing from the parts of a European patent application, seen as a whole, relating to the disclosure (see G 3/89 and G 11/91 mentioned above). Therefore, the complete replacement of the application documents (i.e. description, claims and drawings) by other documents is not possible (see G 2/95).
Some examples of allowable corrections:
The replacement of "respectfully" by "respectively" in a claim (T 34/03
The addition of the plural "s" to the word "particle" as the corresponding verb "have" was in the plural form, and the application as originally filed described a particle size distribution. Since particle size distributions can be defined only for a plurality of particles, the correction was held allowable (T 108/04
On the other hand, the applicant/proprietor cannot rely on:
A mere count of the number of instances of the relevant words in the application as originally filed for obtaining the replacement of one word by another word, for instance the substitution of "included" for "excluded", if it is not clear that an error has occurred and not possible to ascertain that nothing other than "included" was intended by the drafter (T 337/88
Usual practice or industry standards for measuring concentrations of compounds in the relevant technical field, if the application as originally filed merely refers to "%", without clarification as to whether by weight or volume, and the description contains no clear guidance as to whether "%" refers to concentration by % by weight or % by volume or something different (T 48/02
Common general knowledge in the absence of further evidence, such as an encyclopaedia or basic textbook, to argue for instance that the skilled person would have immediately recognised that an ASTM standard with a six-digit number did not exist before the priority date of a patent (T 881/02