The applicant needs always to make clear for which inventions the additional search fees have been paid. Hence, in cases where the applicant pays some, but not all, of the additional requested search fees and fails to indicate for which inventions payments have been made, the search division will make efforts to find out which inventions are to be covered by (an) additional search/searches.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/b_vii_1_2_3.htm
Date retrieved: 17 May 2021