Soft law has for decades played a role in the largely non-harmonized area of EU direct taxation. It more recently appeared in the harmonised area of EU VAT, with the emergence of the VAT Committee guidelines (published since 2012), the adoption of "explanatory notes" by the Commission (for the first time in 2014), and the opinions of the VAT Expert Group (since 2014). Beyond the EU borders, International VAT/GST guidelines are now also being developed under the auspices of the OECD, substantial parts of which have been endorsed by more than 100 states in 2014 and 2015. The objective of this paper is to analyse and assess these four instruments, and to open a discussion on the negative and positive uses that can be made of soft law in an EU harmonised area. The conclusion that we draw from this assessment is that the VAT Committee guidelines and the Commission explanatory notes open the way to "informal governance" in the area of VAT (considered as rather negative) while the VAT Expert Group opinions open the way to an "inclusive" type of governance in this field (considered as very positive).