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Where clarity issues create significant doubt as to the scope of the claims, and consequently of the required search strategy, they should be raised in a similar manner as a lack of descriptive support as discussed above at PCT Articles 5 and 6. Where the claims include alternatives, some of which are unclear realisations of the invention, and it is impossible to determine what may reasonably expected to be claimed, the search may be limited to only clear realisations of the invention. See Art. 6, Art. 15(3), Rule 6.1(a), PCT/GL/ISPE/9 at Chapter 5, Chapter 9 para 9.36-9.37 and Chapter 15.

The procedure for broad claims should also be applied to claims found to lack conciseness, for example, multitudinous claims with overlapping scope. What constitutes an unreasonable number of claims or undue complexity depends on the circumstances of the case but the principle to be applied is that the claims should not be unduly multiplied or duplicative and should not "obscure the definition of the claimed invention in a maze of confusion". The example in para 9.25 of the PCT International Search and Preliminary Examination Guidelines (PCT/GL/ISPE/9) indicates that 480 claims (38 independent) is clearly unreasonable.

PCT/GL/ISPE/9 at Chapter 9, para 9.25 to para 9.30 discusses that where there is significant additional work associated with large and complex claim sets, i.e. in excess of approximately 100-150 (depending on circumstances), and particularly where there is no clear distinction between independent claims because of overlapping scope, it is appropriate to restrict the search to subject matter expected to be claimed and to raise the matter in the written opinion. Where unity of invention is also an issue, the communication with the applicant under MPP Procedures for Informal Communication with the Applicant, and Issuing the Invitation to Pay Additional Search Fees, should be combined.

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