Quote from JohnL111:
Let's say the current bids are:
ARCA - 10K @ 80.20
INET - 10K @ 80.18
AMEX - 50K @ 80.10
If I send a sell limit order to ARCA for 30K @ 80.10 what happens?
ARCA will not trade through the NBBO. For listed stocks the exchanges must suscribe to an antiquated service called ITS.
Your order will execute immediately for 10,000 sh. at ARCA
Then ARCA will check for reserve amounts and discretionary orders on its book. This happen very fast, less than a second.
If no other bids are on ARCA at 80.18 or better ARCA will route to INET.
the best bid in the world is 80.10 AMEX and you still have 10,000 shares to go. Assuming no other bids have come to the market place.
At this point the computer generates an ITS order and sends it to the AMEX specialist to be ignored (OK, they may not ignore it). ITS generates a pop-up window that reads someting like "Order: Sell 10,000 XYZ at 80.10" 15 seconds to respond.
ITS orders can be rejected, partialled, filled, or timed-out.
In theory the exchange is supposed to trade it unless it traded ahead.
If it does not fill it returns to ARCA and begins again.
