2.3 Supplementary international search (SIS) by another office 

When conducting preliminary examination under Chapter II, the examiner must also take into account any documents cited in any supplementary international search report (SISR) by another office which is available in the file.

If the SISR has not been received by the EPO 24 months after the priority date, the file will be sent to the examiner anyway. If, after checking, the examiner concludes that an invitation to pay additional fees in case of lack of unity (see GL/PCT‑EPO C‑V, 1) or a WO‑IPEA (see GL/PCT‑EPO C‑IV, 2.2) has to be sent, this will happen as soon as possible without awaiting the SISR.

If neither an invitation to pay additional fees in case of lack of unity nor a WO‑IPEA needs to be sent out before the IPER is established, the examiner waits until 27 months from the priority date to establish the IPER to allow the SISR to arrive and be taken into account.