Is my understanding correct that IB may not offer price improvement for options unless the order is >50 contracts? http://www.interactivebrokers.com/en/trading/orders/block.php?ib_entity=llc The link says the following: Block Orders Description Block orders can be used for large volume limit orders that consist of at least 50 contracts. Exchanges Native: Simulated (by IB): ISE TWS Links For information on how to create block orders, please refer to the Example You want to buy 10,000 contracts of XYZ for the best possible price. When you transmit the order, use the Order Ticket to select Block Order. This ensures that your order is made public and may result in a price improvement.