The wording of R. 137(5), first sentence, EPC is the same as that of R. 86(4) EPC 1973. R. 86(4) EPC 1973 (with effect from 1 June 1995), was intended to prevent amendments of the application which circumvent this principle that a search fee must always be paid for an invention presented for examination (T 274/03). This rule was introduced to give the EPO the means to react appropriately when the applicant dropped existing claims and replaced them with originally non-unitary subject-matter extracted from the description (see T 1285/11). See also T 1485/13.

In T 274/03 the board stated, with regard to R. 86(4) EPC 1973 (now R. 137(5) EPC), which was introduced with effect from 1 June 1995, that it was intended to prevent amendments of the application which circumvent the principle that a search fee must always be paid for an invention presented for examination. R. 86(4) EPC 1973 stops applicants switching to unsearched subject-matter in the reply to a communication from the examining division and makes means available for the EPO to react when different subject-matter is claimed not simultaneously but in sequence as is the case when the applicant drops the existing claims and replaces them with originally non-unitary subject-matter extracted from the description. See also T 2334/11.

In T 443/97 the board stated that R. 86(4) EPC 1973 (now R. 137(5) EPC) concerned examination proceedings, and particularly those cases in which no further search fees requested by the search division for non‑unitary subject‑matter had been paid by the applicant. The purpose of R. 86(4) EPC 1973 was to exclude any amendment which circumvented the principle according to which a search fee must always be paid for an invention presented for examination. The board noted that unity of invention was a requirement of an administrative nature and that the administrative purposes of this requirement were fulfilled when the examination procedure had been concluded, i.e. when the patent had been granted (see G 1/91, OJ 1992, 253). Therefore, R. 86(4) EPC 1973 was not relevant for the opposition case in hand.

In T 442/11 the board observed that R. 137(4) EPC, as in force before 1 April 2010, (having the same wording as R. 86(4) EPC 1973) had entered into force on 1 June 1995 and been incorporated in the Implementing Regulations to prevent applicants from switching, during the examination proceedings, the protection sought to unsearched parts of the application which had not yet been claimed when the search was performed (see "travaux préparatoires" on R. 86(4) EPC 1973, OJ 1995, 409). See also T 509/11, T 2334/11, T 1485/13, T 145/13.