IEX Opening and Closing Auctions

The IEX Auction Process provides electronic price discovery mechanisms that efficiently match orders in IEX-listed securities at a single price using a double auction. These auctions enable IEX participants to execute against On-Open and On-Close interest at IEX. During the auction process, IEX will calculate and disseminate current price, size, imbalance information, auction collar information, and other relevant information about upcoming auctions. For details about all IEX Auctions, please see the IEX Auction Specification.

Please see the IEX Opening and Closing Auction Quick Guide for a printable summary of the relevant information for the IEX Opening and Closing Auctions.

Opening and Closing Auction Times

Opening Auction Closing Auction
8:00 a.m. Trading and order entry begins
Lock-in Time
9:28 a.m. Dissemination of Auction Information begins
On-Open and queued orders are locked into the auction
3:50 p.m. Dissemination of Auction Information begins
On-Close orders are locked into the auction
Lock-out Time
9:29:50 a.m. On-Open orders are rejected on entry 3:59:50 p.m. On-Close orders are rejected on entry
Auction Match
9:30 a.m. The Opening Auction match occurs 4:00 p.m. The Closing Auction match occurs
5:00 p.m. Trading and order entry ends

(All times are Eastern)

Security Eligibility

Only IEX-listed securities are eligible for IEX Auctions. Listings on IEX will be added to the Opening and Closing Auctions either after an IPO Auction or after the listing has transferred to IEX from another listing exchange. On-Open and On-Close orders submitted for non-IEX-listed securities will be rejected.

Order Types

Highlighted below are the order types accepting during the IEX Opening and Closing Auctions. Please refer to the IEX FIX Specification for details on submitting such orders.

Opening Auction
On-Open Orders Specifically request an execution at the opening price
  • Limit-On-Open (LOO) or Market-On-Open (MOO)
Queued Regular Hours Orders Orders executable from 9:30 a.m. to 4:00 p.m., including during the Opening Auction
  • Includes limit DAY or GTX orders, and non-routable market DAY orders queued before the Opening Auction
Closing Auction
On-Close Orders Specifically request an execution at the closing price
  • Limit-On-Close (LOC) or Market-On-Close (MOC)

Note that IEX does not support an Imbalance Only order type. Members can use LOO and LOC orders after the Lock-in Time to offset the published imbalance.

Imbalance Data

The IEX Auction Information provides transparency that allows for increased liquidity and better trade performance. IEX Auction Information can have a positive impact on traders’ ability to perform effectively in a competitive environment by providing users with valuable details about the opening and closing orders and the likely opening and closing prices of an IEX-listed security.

IEX disseminates Opening Auction information every one second between 9:28 and 9:30 a.m., and Closing Auction information between 3:50 and 4:00 p.m. This data is available FREE of charge via IEX products, in addition to other third-party providers:

Firms should contact their market data vendors and service bureaus directly regarding the availability of IEX Auction Information and On-Open/On-Close order types.

Please see the IEX Opening and Closing Auction FAQs to answer any remaining questions.