RE:Understanding MOC 101---pleasefisher, read this document. It make it clearer for me. an intereesting part of the document: ------- Closing Price One of the most important (and widely used) benchmarks in the industry is the closing price. There are a number of reasons for the popularity of the closing price. It is simple to calculate, it provides the price where the buyers/sellers value the stock at the end of the trading session, and it is widely pub-lished to name a few. Due to these reasons, many participants use the closing price for valuation purposes. Index providers use closing prices for rebalancing to determine levels where stocks get added/deleted. Mutual funds use them to value portfolios and for cash inflow/outflow pricing. Portfolio managers and analysts use them for portfolio modelling and data studies that can span years due to the ease of availability. The popularity of the closing price as a benchmark does however present some problems with trading. It is a single price point which a lot of participants want to trade at and is susceptible to volatility; ie a small amount of trading has the potential to drastically change the valuation of portfolios, indices etc. This is primarily why regulators monitor activity around the close very carefully to ensure closing prices are fair. MOC Facility------ https://qes.bmocm.com/papers/18_BMO_MarketOnClose.pdf