The supplementary international search system is optional for both applicants and International Authorities. Its purpose is to enable applicants, during the international phase, to obtain further supplementary searches from other Authorities so that they have a better basis for deciding whether or not to enter the regional phase.[Rule 45bis; OJ EPO 2017, A115; OJ EPO 2018, A24; GL/ISPE 2.20; 15.76; ]

The EPO as SISA only accepts a limited number of SIS requests per year. Since 2010, the EPO has limited the number of SIS requests it will accept to 700 per year.