A claim's subject-matter is normally defined in terms of positive features indicating that certain technical elements are present. Exceptionally, however, the subject-matter may be restricted using a negative limitation expressly stating that particular features are absent. This may be done e.g. if the absence of a feature can be deduced from the application as filed.
Negative limitations such as disclaimers may be used only if adding positive features to the claim either would not define more clearly and concisely the subject-matter still protectable or would unduly limit the scope of the claim. It has to be clear what is excluded by means of the disclaimer. A claim containing one or more disclaimers must also fully comply with the clarity and conciseness requirements of Art. 6.
For the allowability of disclaimers excluding embodiments that were disclosed in the original application as being part of the invention, see GL/PCT-EPO H‑III, 4.2. With respect to the allowability of a disclaimer not disclosed in the application as filed see GL/PCT-EPO H‑III, 4.1.
The EPO applies option GL/ISPE A20.21 of the Appendix to Chapter 20 of the ISPE Guidelines.