Our paper analyses the characteristics of firms that disclose information about Corporate Social Responsibility, under the guidelines of Global Reporting Initiative (GRI) or other formats. We focus our research into committed reporting proxied by the use of GRI standards (where firms mention at least one GRI indicator) and compare with firms that also disclose some CSR activities but do so in an opportunistic fashion. We collect data from top 500 Portuguese firms that disclose information about CSR. The final data set includes 123 firms that disclose some report concerning CSR. We don't find a linear association between those characteristics and committed reporting, except for group affiliation. In fact, we extend previous literature to show that multiple configurations, using Fuzzy-set Qualitative Comparative Analysis (fsQCA), relate to committed sustainability reporting, providing justification for the mixed results obtained in previous research. Using fsQCA, we argue that committed CSR reporting associates with profitability and group affiliation where the parent company reports for the entire group (cost efficiency), along with external auditing of the report. Once we exclude auditing, committed CSR reporting is strongly influenced by group reporting but also by nonpolluting industries settings, where regulation and scrutiny aims the opposite.