According to the FATF recommendation 20, all persons in the regulated financial sector are subject to the duty to make a suspicious transaction report (STR). They must know their client and their business. Furthermore, they must be aware of the risks associated with money laundering and terrorist financing through specific training to increase their awareness in this field.Therefore, a person subject to this recommendation must file an STR after reviewing elements on an account that raised suspicion in his mind such as an abnormal transaction volume, the refusal of a client to provide supporting documents. Thanks to his knowledge of the client and his activity and all the risks related to ML/TF, a person can complete an STR rationally on reasonable grounds of suspicion. A person guessing just based on inaccurate assumptions might be speculating on a doubt. Hence, the objective test of knowledge or suspicion must determine the transition from a subjective to an objective suspicion due to rational foundations and elements that raised red flag indicators. However, a person that fails to make an STR while he knows about it and hides his suspicion; he commits professional misconduct punishable by law. It means that he voluntarily remained in the ignorance of crucial elements to avoid reporting this transaction and can be accused of willful blindness. This principle, used by law, means that a person has voluntarily remained in ignorance about elements to hide a criminal liability. This type of situation can have serious financial consequences and also on the reputation of a financial institution or even its closure. The New Zealand Society articles depict the judgement sentence of the director of Pin Han Finance LTD in New Zealand. He fails to verify the identity of 372 customers and miss to report 172 suspicious transactions. The default of due diligence and STR resulted in a fine of $ 5.29 million, 6 months in jail and 200 hours of general work for the director and therefore its liquidation.