A short but important ESMA Discussion Paper was issued at the end of December entitled "Share classes of UCITS". It seems to go to the question "What is a sub-fund?" as much as "What is a share class?"
It all used to be very simple with single UCITS funds with a single pot of assets and a basic selection of share classes – essentially only income and accumulation options. With the popularity (and indeed now predominance) of umbrella funds with a number of sub-funds and the proliferation of share classes, it seems from the ESMA Discussion Paper that some products being established in the market place now have lost some of the basic notions of a UCITS retail investment fund.