Any size stock order, even if it is not in a round lot increments, can be submitted using a MOO, LOO, MOC or LOC order type. When you SMART route an At-the-Opening or At-the-Close order type, it will be routed to that symbol's primary listing exchange and given to the Specialist. There is never a guarantee that the Specialist will have enough shares available to match all the Buy and Sell orders they receive for an opening or closing cross. Orders are filled on a priority basis with the earliest submitted Market-on-Open orders filled first. If there are any shares still available to cross, the marketable Limit-on-Open orders with the earliest time stamps are next in line. If your order did not get filled, then there were not enough shares available for all of the orders submitted for the Opening or Closing cross trade.
The NYSE’s Opening and Closing Auction information can be found by clicking here.
The Nasdaq's Opening and Closing Cross information can be found by clicking here.
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