It stands for minimum quote size; on the London Stock Exchange (LSE), it refers to the minimum number of shares in which market makers are registered and obliged to trade and display prices on the stock exchange automated quotation system (SEAQ). Likewise, the American stock exchange NASDAQ also used to impose a similar regulatory requirement. This minimum was usually dodged by certain high level NASDAQ executives in the event that the price per share is more than $200. The Actual Size Rule repealed the regulatory minimum quote size (1000 shares).

In essence, the mandatory quote size requirements were designed “to ensure an acceptable level of market liquidity and depth in a trading environment where market makers were the only market participants who could impact quotation prices. However, these requirements were repealed in order to remove unnecessary competitive burdens and therefore to level the playing field between primary markets in the U.S. In addition, the lowering of the minimum quote size to one normal unit of trading (i.e., 100 shares) aimed to remove an unnecessary barrier to entry by making it less capital intensive for broker-dealers to function as market makers in NASDAQ stocks”.