The harm test in access to information law is an interpretive tool to reduce discretional decisions in the classification of information. In Mexico, the regulatory framework takes as a reference the principle of proportionality for the application of the test; however, it is necessary to clarify the reasons and standards of the said to understand the methodology through which the argumentation to ground the closure of information must be carried out. Without this method, the exercise of testing harm will remain discretionary on the side of the government agencies.