Recent changes made by European countries have paved the way for Monaco to become more transparent.
For several years, Monaco has been listed as an uncooperative tax haven by the OECD, along with Andorra and Liechtenstein. It's not that the Principality refuses to provide any personal banking and tax information whatsoever, just that it's only given to judges as part of an investigation. There's no automatic exchange of information between tax authorities, and Monaco has been reticent to increase transparency while other countries such as Austria and Luxembourg, both members of the EU, continue to practice secrecy.
That all changed earlier this month when Liechtenstein and Andorra announced they would relax their banking secrecy laws, closely followed by Switzerland, Austria and Luxembourg. It seems they were all worried about being placed on a blacklist by the G20 countries who are meeting in London next week.
In the face of this trend to become more open, the Principality is now also discussing further cooperation with the OECD in order to make banking and taxation systems more transparent.