Choice of ISA and consequences
If the receiving Office has specified more than one ISA, the applicant must indicate his choice of ISA in the PCT request (Box No. VII) and in the Fee Calculation Sheet (Box No. 2) (see Annex VII). Only one ISA may be selected. For example, the EPO may be chosen as ISA for applications filed with the USPTO and for applications in English filed with the JPO as receiving Office.
Agreement EPO-WIPO, Art. 3(2), Annex A(ii) 
OJ 2010, 304
Applicants considering their choice of ISA are advised to bear in mind that the EPO will act as an IPEA only if the international search was carried out by the EPO itself or by any other "European ISA". On 1 January 20142015, the EPO, the Austrian, Finnish, Spanish and Swedish patent offices and the Nordic Patent Institute were acting as European ISAs (see point 307).
If the EPO acts as ISA or SISA, the supplementary European search report is dispensed with and so no search fee will be due on entry into the European phase (see point 572).
OJ 2009, 594
OJ 2012, 584
If the EPO acts as IPEA, a reduction of 50% in the fee due for examination in the European phase is granted (see point 593).

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