can dark pools distinguish between a sell order to close, or a short order to open?

can dark pools distinguish between a sell order to close, or a short order to open?

or market makers for that matter?

 

Your broker to be Reg SHO compliant is required to tag sell orders as SELL or SELL SHORT. So, I'm not sure why you are asking but yes they can.

 

Do they also tag - buy to open, or buy to close(cover short)?

 

I am wondering why some orders are filled and others aren't - when I am trading both sides of the market.

 

That is the correct way to send a buy order with that tag. If not it can be booked incorrectly and you can end up with a boxed positions as buy to open is booked to the TYPE 1 CASH account for CASH accounts, TYPE 2 MARGIN account for Margin accounts buy to close offsets a short position in TYPE 3 SHORT account.

 

Honestly, I'm not sure why the DARK pool would care. They only make money when they pair off both sides.

 

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Depends\ on liquidity;
+limit orders= always risky ,not to get filled
+ the occasional tight trender day, not many pullbacks long or short[inverse ETFs, about the same thing....... ]
I seldom mess or miss with a limit order on exits, sometimes i do; especially with a overnite resting order.
I'm sure MM tag or note a buy to open or a buy to close , for hedging. Especially since its 100% different position............................

 

Does the exchange send out this data with their trade data? I took a look at trade conditions and don't see anything that differentiates SELL or SELL SHORT. But trade conditions are complex. Or does this data stay away from public view?

 

The entire point of a dark pool is to be dark. It is not in the public view besides the trade prints.

 

Sorry, I meant the trade prints from all exchanges. Do they indicate which trades had a short sell when matched?