An “Odd Lot” is a stock order comprised of less than 100 shares of stock. Any stock order from 1 share to 99 shares is considered to be an odd lot.
Odd-Lot orders to initiate positions will not be routed to primary exchanges.
Odd-Lot orders can be routed to primary exchanges, but only if the order in question is to close out a pre-existing position.
IBKR will not direct-route odd-lot orders which initiate positions to primary exchanges, therefore these type of orders should be Smart Routed so that IBKR’s routing system can send the order to an ECN for execution. The exception is that odd lots can be routed to NYSE/ARCA/AMEX, but only as part of a basket order or as a market-on-close (MOC) order.
Odd-Lot orders are not posted to the bid/ask data on exchanges.
Odd-Lot orders are taken into the order book at the exchange they are routed to. When the exchange is able to match an order from the other side of the book with the odd-lot, it will be filled. This could lead to a delay of the execution of an odd-lot.
The low/high price reflected by the exchange take only trades of more than 100 shares, that’s why you can sometimes get a buy fill above the official high of the day (odd lot).