Opening Imbalance Only Order (OIO)

WHAT IS AN Opening Imbalance Only Order (OIO)

Opening Imbalance Only Orders (OIO) are a type of limit order that provides liquidity during the opening cross on the Nasdaq. A limit order is an order placed with a brokerage to execute a buy or sell transaction at a set number of shares and a specified limit price.

BREAKING DOWN Opening Imbalance Only Order (OIO)

Opening Imbalance Only (OIO) orders are only executable on the opening cross and are not displayed or disseminated. OIO buy orders only execute at or below the 9:30 a.m. bid price, while OIO sell orders only execute at or above the 9:30 a.m. offer price. OIO orders must necessarily be limit orders, and market OIO orders are not permitted. Since OIO orders are only executable during the opening cross, they are not at risk of being executed prior to market open, unlike continuous market orders.

OIO buy or sell orders priced more aggressively than the 9:30 a.m. Nasdaq highest bid or lowest offer prior to market open will be re-priced to the Nasdaq bid or offer before the opening cross is executed.

So, for example, if an OIO buy order price is $9.95 and the Nasdaq bid is at $9.93, the OIO order will be re-priced to $9.93. This adds liquidity to the market and helps ensure that Market-On-Open (MOO) and Limit-On-Open (LOO) orders are properly executed.

OIO orders are accepted on the Nasdaq from 7 a.m. onward. However, market participants cannot update these orders after 9:28 a.m., although new OIO orders can still be entered after that time.


Opening Imbalance Only Orders (OIOs) are executed within the Nasdaq. Nasdaq is a global electronic marketplace for buying and selling securities, and also serves as the benchmark index for U.S. technology stocks. The National Association of Securities Dealers (NASD) created Nasdaq to enable investors to trade securities on a computerized and transparent system. In 2006, Nasdaq officially separated from the NASD and began to operate as a national securities exchange.

The term Nasdaq is also used to refer to the Nasdaq Composite, which is an index of more than 2,500 stocks listed on the Nasdaq exchange that include some of the world’s largest technology and biotech giants such as Apple, Google, Microsoft, Oracle, Amazon, Intel and Amgen.

Nasdaq has been a leader in trading technology from its inception. The Nasdaq computerized trading system was initially devised as an alternative to the inefficient specialist system, which had been the prevalent model for trading for nearly 100 years. Today, due to rapid technological advancements, Nasdaq’s electronic trading model is the standard for markets worldwide.

Article Sources
Investopedia requires writers to use primary sources to support their work. These include white papers, government data, original reporting, and interviews with industry experts. We also reference original research from other reputable publishers where appropriate. You can learn more about the standards we follow in producing accurate, unbiased content in our editorial policy.
  1. Nasdaq. "The Nasdaq Opening and Closing Crosses," Pages 1-2. Accessed April 21, 2021.

  2. Nasdaq. "NASDAQ Opening and Closing Crosses," Pages 1-2. Accessed April 21, 2021.

  3. U.S. Securities and Exchange Commission. "Release No. 34-84386," Page 2. Accessed April 21, 2021.

Open a New Bank Account
The offers that appear in this table are from partnerships from which Investopedia receives compensation. This compensation may impact how and where listings appear. Investopedia does not include all offers available in the marketplace.