Nasdaq Sell Imbalance-Only Orders in the Closing Cross
Summary
The discussion explains Nasdaq Sell Imbalance-Only orders, which are limit orders intended to provide liquidity against orders participating in the closing auction. The cited description says sell IO orders execute only at or below the closing-time bid or ask condition specified for the order type, and that market IO orders are unavailable. A limit set well below the prevailing market can therefore make execution more likely while retaining the auction’s price conditions.
The answers relate this order type to a trading approach that seeks to trade against closing imbalances and offset exposure in the Closing Cross. One answer describes driving the continuous-market price and covering in the auction, while noting that an imbalance moving the other way can cause substantial losses. The example reports a large sell fill above the recent best offer, but this isolated event does not establish general profitability or fully verify the proposed strategy explanation.
Key ideas
- Sell Imbalance-Only orders are limit orders designed to provide liquidity in Nasdaq’s Closing Cross.
- The order’s limit price governs execution eligibility relative to the closing auction price conditions.
- A low sell limit may increase the chance of execution while still being an order with a price limit.
- Trading around closing imbalances can expose a strategy to losses when the imbalance shifts against it.
- A single reported fill is not evidence that the strategy is consistently profitable.
Tags
Full text
# What are Sell Imbalance-Only Orders? # What are Sell Imbalance-Only Orders? I am reading the 2014 SEC filing against Athena, a HFT firm. (http://www.sec.gov/litigation/admin/2014/34-73369.pdf) At point 29, they describe the behavior of Athena moments before market closing time. I am confused by 3:50:00.578. What are Sell Imbalance-Only orders? Why are they priced at only $0.01? And how do they help in Athena's profits? Thanks ## Answer by pyCthon (score 2) https://quant.stackexchange.com/a/18390 From the Nasdaq page, > IMBALANCE-ONLY CLOSE ORDERS Provides liquidity intended to offset on-close orders during the Closing Cross. Must be priced (limit), no market IO orders. IO buy/sell orders only execute at or above/below the 4:00 p.m., ET, bid/ask. They simply mean they were +\$0.01 or at \$23.56 from the price on their sell Imbalance-Only orders. The same notation is used shortly after, > 4:00:03.348 – NASDAQ ran its Closing Cross auction. Athena’s Sell Imbalance-Only Orders were filled by selling 233,979 shares for \$23.61, \$.03 or 13 bps, higher than the best offer in the milliseconds prior to Gravy. ## Answer by Jason Nordwick (score 1) https://quant.stackexchange.com/a/18401 From what i understand about Athena's strategy, they always wanted to execute on the imbalance. They would drive the continuous price in one direction and cover in the cross at an in-/de-flated price. Setting the sell price of an imbalance only order would basically be like sending a market order and give them the best chance of executed on the imbalance at close. That's how i understood it, but a few things still don't make sense to me. It sounds like time shifting arbitrage, even if it wasn't pursued with the noblest of intentions. I've run strategies that participated in the cross but don't know profitable this could have been. They did lose big on this too, which sounds definitely likely if the imbalance moves the other way on you.
Shown in full with attribution under the source's licence. Licence: CC BY-SA 4.0 (Stack Exchange)
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.