This work aimed to investigate the necessary and sufficient evidence to attest to the typical predecessor offence in the crime of money laundering, considering that no criminal investigation or prior conviction is required in relation to the predecessor offence in the crime of money laundering under the Brazilian legal system, having as comparative law Portugal and Spain, in addition to trials relating to the three countries in question. It is based on a case study in Spain, judged by the Spanish Supreme Court as a comparative basis. Throughout the Report, the conditions for the certainty of the typical illicit background to the conviction in the crime of laundering are discussed, as well as the analysis of the typical elements necessary to prove it.