The "problem and solution approach" is regularly applied by the departments of the EPO in the course of deciding whether or not claimed subject-matter fulfils the requirements of Art. 56 EPC. This consists essentially of

(a) identifying the "closest prior art",

(b) assessing the technical results (or effects) achieved by the claimed invention when compared with the "closest state of the art" established,

(c) defining the technical problem to be solved as the object of the invention to achieve these results, and

(d) examining whether or not a skilled person, having regard to the state of the art within the meaning of Art. 54(2) EPC, would have suggested the claimed technical features in order to obtain the results achieved by the claimed invention (see e.g. T 939/92, OJ 1996, 309; T 15/93; T 433/95; T 917/96; T 631/00; T 423/01; T 215/04; T 1621/06; T 1183/06; T 824/07; see also Guidelines G‑VII, 5 – November 2018 version).

On application of the problem and solution approach to claims comprising technical and non-technical aspects (especially in the case of computer-implemented inventions), see in this chapter I.D.9.1., and for its application to claims directed to chemical inventions, see in this chapter I.D.9.8.1.

The boards frequently cite R. 42(1)(c) EPC as the basis for the problem and solution approach. R. 42(1)(c) EPC requires that the invention be disclosed in such terms that the technical problem (even if not expressly stated as such) and its solution can be understood. Problem and solution are thus component parts of any technical invention. The problem and solution approach was primarily developed to ensure objective assessment of inventive step and avoid ex post facto analysis of the prior art.

A solution claimed as non-obvious is patentable only if it actually has the alleged effect. According to T 2001/12, a doubt that the invention as claimed is capable of solving the problem defined in the application may have the following consequences: a) If the question arises because the claim fails to specify those features which are disclosed in the application as providing the solution to the problem, then the description and claims are inconsistent in relation to the definition of the invention, and an objection under Art. 84 EPC 1973 may properly arise that the claims do not contain all the essential features necessary to specify the invention. b) If this is not the case, but, having regard to the prior art, and irrespective of what may be asserted in the description, it does not appear credible that the invention as claimed would actually be capable of solving the problem, then an objection under Art. 56 EPC 1973 may be raised, possibly requiring a reformulation of the problem. See also T 862/11 which also dealt with the distinction between the requirements of sufficiency of disclosure (Art. 83 EPC), clarity of the claims (Art. 84 EPC), and inventive step (Art. 56 EPC).

According to the case law of the boards (see T 1/80, OJ 1981, 206; T 20/81, OJ 1982, 217; T 24/81, OJ 1983, 133; T 248/85, OJ 1986, 261), the assessment of inventive step has to be based on the objective, not subjective, achievement of the inventor. By starting out from the objectively prevailing state of the art, the technical problem is to be determined on the basis of objective criteria and consideration given to whether or not the disclosed solution is obvious to the skilled person. Although the problem and solution approach is not mandatory, its correct application facilitates the objective assessment of inventive step. The correct use of the problem and solution approach rules out an ex post facto analysis which inadmissibly makes use of knowledge of the invention (T 564/89, T 645/92, T 795/93, T 730/96, T 631/00). In principle, therefore, the problem and solution approach is to be used; however, if exceptionally some other method is adopted, the reasons for departing from this generally approved approach should be stated.

In T 967/97 the board stated that the problem and solution approach was essentially based on actual knowledge of technical problems and ways to solve them technically that the skilled person would, at the priority date, be expected to possess objectively, i.e. without being aware of the patent application and the invention that it concerned (see also T 970/00, T 172/03).

In T 2517/11 the board held that the fact that a technical feature of a known method was "hidden" – i.e. implicit in a prior-art document and not identifiable on a mere reading of that document – and could be detected only by way of a mathematical analysis did not mean that it could not be taken into account as a disclosed feature. If an analysis revealed such a "hidden" feature, that showed it was publicly available; whether there had been any objective reason to carry out the analysis was irrelevant (with reference to G 1/92, OJ 1993, 277). This followed from the objective nature of the problem and solution approach developed in the boards' case law, which entailed consideration of all technical features comprised in the closest prior art, regardless of whether they were directly identifiable or hidden, since even hidden features were publicly available.

The board in T 1761/12 held that the problem and solution approach involved analysing the steps the skilled person would have taken to solve the predefined objective technical problem, and nothing else. Any further reflection on whether the associated changes to the closest prior art identified in this analysis made sense had the effect, in practice, of adding the related aspects of other problems to the objective technical problem initially defined.

In T 320/15 the board held that the problem and solution approach did not consist of a forum in which the appellant (opponent) could freely develop various attacks based on diverse prior-art documents in the hope that one of them would succeed.

Instructive summaries of the case law on the problem and solution approach can be found in a number of decisions; see e.g. R 9/14, T 519/07, T 698/10.

According to the board in T 270/11, the problem and solution approach does not require that the application specify what feature is responsible for producing precisely what advantage or technical effect. All that is required for inventive step is that the claimed subject-matter is not obvious to the skilled person in the light of the prior art (Art. 56 EPC). It is common practice to take features from dependent claims or the description and insert them into an independent claim with a view to rendering the subject-matter patentable and to cite the effects and advantages associated with those features as a basis for (re-)formulating the technical problem. To determine the objective technical problem, the technical results and effects achieved by the claimed invention as compared with the closest prior art must be assessed.

In T 188/09 the board noted first that whatever approach was applied as an auxiliary means for the evaluation of inventive step of claimed subject-matter, in a given evidential situation it had to provide the same result, be it either in favour of or against inventive step. Therefore, even if the "problem and solution approach" was applied, the decision on inventiveness should be the same as if it had not been used. Citing T 465/92 (OJ 1996, 32), the board observed: "if an invention breaks new ground it may suffice to say that there is no close prior art rather than constructing a problem based on what is tenuously regarded as the closest prior art."

In T 465/92 (OJ 1996, 32) the board did not take the problem and solution approach when assessing inventive step, and said this was merely one possible approach, with advantages and drawbacks. It took the view that all of the seven relevant citations came equally close to the invention. See also T 967/97 in the chapter I.D.3.1. "Determination of closest prior art in general".

In case R 5/13 (as well as R 9/13, R 10/13, R 11/13, R 12/13 and R 13/13 which were all directed against T 1760/11), the petitioners argued that they should have been allowed to discuss all the issues of inventive step of any stage of the problem and solution approach in respect of all possible starting points that they wished to rely on, despite the fact that the board had structured the discussion by first establishing which document or documents constituted the most promising starting point. The Enlarged Board in R 5/13 held that the board had not only followed the sequence for the debate announced in its communication annexed to the summons to oral proceedings, but by doing so it had also systematically applied the standard method of the problem and solution approach. The Enlarged Board stated that the examination whether or not the subject-matter of a patent claim involved an inventive step according to the well-established problem and solution approach was a matter of substantive law. That was equally true for the determination of the closest prior art as the first step of the problem and solution approach, whether one document alone or a plurality of documents was taken as the starting point or most promising springboard aiming at the invention.