Unpriced order auction and routing

1. A A method comprising:

scheduling, by a computer system comprising at least one processor and non-transitory memory storing executable program code, a single-price auction for shares of an issue to occur intra-day at a scheduled auction time concurrently with and separately from a continuous matching process executed by a continuous matching engine of the computer system;

receiving, by an order and execution interface of the computer system, a plurality of electronic orders comprising one or more limit orders that include a specified price and one or more unpriced orders that do not include a specified price;

automatically directing, by the order and execution interface, the one or more limit orders to the continuous matching engine and the one or more unpriced orders to an unpriced order auction engine of the computer system;

continuously updating and disseminating in real-time, by the unpriced order auction engine, until the scheduled auction time, an auction imbalance volume comprising a difference between an aggregate volume of the one or more unpriced orders to buy shares and an aggregate volume of the one or more unpriced orders to sell shares;

responsive to disseminating the auction imbalance volume, receiving, by the order and execution interface, one or more of the following responses until the scheduled auction time: one or more new unpriced orders, one or more cancellations of previously received unpriced orders, and one or more instructions requesting modifications to previously received unpriced orders;

updating, by the unpriced order auction engine, the auction imbalance volume based on the received one or more responses until the scheduled auction time; and

executing, by the unpriced order auction engine, the single-price auction at the scheduled auction time, wherein the continuous matching process is not interrupted by the single price auction at any time before or during the single-price auction, by:

determining, by the unpriced order auction engine, a single auction price comprising a midpoint of a national best bid and offer (NBBO) quote; and

executing, by the unpriced order auction engine, at the determined single auction price, one or more trades of the one or more unpriced orders to buy shares matched with the one or more unpriced orders to sells shares.

2. The method of claim 1 , wherein the continuous matching engine is configured to immediately execute a portion of the one or more limit orders at the specified price.

3. The method of claim 2 , wherein the portion of the one or more limit orders are marketable against a public order book.

4. The method of claim 3 , further comprising:

storing, by the order and execution interface, the one or more unpriced orders in an unpriced auction order book that is separate from the public order book.

5. The method of claim 1 , further comprising:

automatically routing, by the unpriced order auction engine, a second portion of the one or more unpriced orders, consisting of unpriced orders other those in the first portion of the one or more unpriced orders, to the continuous matching engine.

6. The method of claim 5 , further comprising:

executing, by the continuous matching engine, the continuous matching process on the second portion of the one or more unpriced orders.

7. The method of claim 5 , further comprising:

determining, by the unpriced order auction engine, a maximum matchable quantity comprising a lesser of an aggregate buy volume and an aggregate sell volume;

determining, by the unpriced order auction engine, an auction imbalance quantity comprising a difference between the maximum matchable quantity and a greater of the aggregate buy volume and the aggregate sell volume; and

matching, by the unpriced order auction engine, the first portion of the one or more unpriced orders up to the maximum matchable quantity.

8. The method of claim 7 , further comprising:

determining, by the unpriced order auction engine, whether the NBBO quote is crossed; and

responsive to the determining that the NBBO quote is crossed, discarding, by the unpriced order auction engine, the crossed NBBO quote and evaluating a next NBBO quote.

9. The method of claim 7 , further comprising:

determining, by the unpriced order auction engine, whether the NBBO quote is locked; and

responsive to the determining that the NBBO quote is locked, setting, by the unpriced order auction engine, the single auction price as the lock price of the NBBO quote.

10. The method of claim 7 , further comprising:

determining, by the unpriced order auction engine, whether the NBBO quote is locked; and

responsive to the determining that the NBBO quote is locked, discarding, by the unpriced order auction engine, the locked NBBO quote and evaluating a next NBBO quote.

11. The method of claim 1 , further comprising:

determining, by the unpriced order auction engine, whether a posting market center has market makers assigned to the issue in the single-price auction and whether the market makers publish quotes in the issue; and

responsive to the determining that the posting market center has market makers assigned to the issue in the single-price auction and that the market makers publish quotes in the issue, excluding, by the unpriced order auction engine, the quotes published by the market makers from the single-price auction.

12. The method of claim 1 , further comprising:

determining, by the unpriced order auction engine, whether a posting market center has market makers assigned to the issue in the single-price auction and whether the market makers publish quotes in the issue; and

responsive to the determining that the posting market center has market makers assigned to the issue in the single-price auction and that the market makers publish quotes in the issue, making, by the unpriced order auction engine, unpriced orders that do not execute in the single-price auction eligible for execution against contraside market maker quotes.

13. The method of claim 1 , wherein the scheduled auction time occurs after an opening of trading on a primary listing market center of the issue and before a close of trading on the primary listing market center of the issue.

14. The method of claim 1 , further comprising:

continuously updating, by the unpriced order auction engine, the auction imbalance volume based on, at least, the received one or more responses.