When is it useful to file a demand for international preliminary examination?

An international preliminary examination gives you the opportunity to respond to any negative finding of the EPO acting as ISA while you are still in the international phase under the PCT, which might avoid that you have to draft and file multiple responses with the national/regional offices upon entry into their national/regional phases. Therefore, if you believe that you can overcome the examiner’s objections by filing amendments and/or arguments which could lead to a "positive" international preliminary examination report, it is useful to file a demand for international preliminary examination under PCT Chapter II,

Where you select the EPO as IPEA, you will benefit from a 75% reduction in the examination fee payable to the EPO as designated or elected Office when entering the European phase.

However, if the EPO acting as ISA has issued a declaration under Article 17(2) PCT that an ISR could not be established ("declaration of no search"), filing a demand is not recommended, since the EPO cannot examine an application for which no search has been carried out.