The strategy I build and test uses MOO orders. There are many reasons why I need exactly that order to make my strategy robust. My broker is "Interactive Brokers". Recently I've found on their site something about MOO and MOC order with odd lot. I've called to support. And I have long explanation why NYSE cannot fill odd lot and my order will be canceled - "NYSE does not have an odd lot order book", "if and only if there will be odd lot to sell I can buy", etc... I've contacted MBTrading with the same question: "If there is any restriction on MOC, MOO orders". They told me - "none that I'm aware of". After that I've asked IB again direct question : "How can I buy 50 shares of SPY with MOO order" And got an answer - "SPY has ARCA has the primary, not the NYSE. ARCA accepts odd lots". And something that I totally don't understand (my conversation with IB): What the hell is ARCA and NYSE Arca ???? Can somebody elaborate on the rules of MOO with odd lots. Maybe I need to change a broker? P.S. Why odd lots are so important to my trading and why I cannot work with round lots. For example I buy round lot 100 shares for 112$ each. I've got profit of 2.5$ per share. My next deal must be 102 shares - not 100, not 200 but exactly 102.