The Recommendations of the Financial Action Task Force (FATF) revised in February 2012 include “tax crimes (related to direct taxes and indirect taxes)” in the list of “designated categories of offences”. Thus, states are encouraged to include a range of tax offences in their definition of predicate offences. However, the standards defined by FATF are not compulsory, and they are framed in a fairly supple manner, allowing the national lawmakers to limit money laundering to the proceeds of serious offences and to decide how they will define the predicate offences and any elements that make them serious. The pressure on Switzerland to define predicate crimes in tax matters must nevertheless be considered as strong, since many countries already consider that money laundering can be committed in relation to such crimes and strive to create a level playing field for the financial industry. This contribution reflects on how serious tax offences could be defined with the aim not only of satisfying the international standards, but also and foremost, of giving adequate assistance and protection to Swiss criminal enquiries in tax matters. It then analyses how the requirement that the laundered assets are “proceeds” of the predicate offence could be dealt with in this context. Finally, it evaluates the possible impact of the creation of predicate tax crimes on the due diligence duties of financial intermediaries.