The aim of this article is to reconstruct in a rational way the use of the proportionality test in contexts of constitutional social rights adjudication. Such a reconstruction will be developed in two steps. Firstly, I will address the question as to whether proportionality test in its “by omission” version (i.e. used to apply positive rights) shows or not a different structure in comparison with its, much better known and investigated, “by excess” version (i.e., used to apply negative rights). Secondly, I will describe the rules and forms of reasoning that are implied in the use of proportionality test by omission and integrate, respectively, the sub-tests of suitability, necessity and proportionality stricto sensu. Finally, I will present a brief summary as a conclusion.