LULD rules - help please

T

terr

Not sure which forum to put this into.

I have been reading LULD regulations trying to figure out how to calculate the limits. Tell me if I am correct.

The price band % calc is pretty clear - depends on time of day, previous close and Tier1/Tier2 designation.

The limits are calculated as the price band % offset from Reference Price. Reference Price seems to be defined as an SMA of all trades over the previous 5 minutes - but it is set at opening and is not continuously adjusted but is ratcheted in 1% increments up/down? Is the SMA done on minute boundaries or is it a continuously tracking one? Do I have to keep two reference prices - one the SMA one and the other the ratchet one?

Seems like there is no way to calculate a real LULD unless you either backfill (and, what's more - tick-backfill) at least five minutes for the stock and keep the averages updated as the trades come in?
 
Here's an example calculation: http://www.luldplan.com/

"When the National Best Bid (Offer) is below (above) the Lower (Upper) Price Band, the SIPs disseminate the National Best Bid (Offer) with an indicator identifying it as unexecutable."

I wonder how this affects stop-loss orders that go directly to the exchange (instead of waiting at the brokerage firm).
 
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Implemented it as an indicator on chart.. Looks about right:

upload_2020-8-21_12-25-40.png
 
Don't know - the Reference price is adjusted by taking a 5 min SMA of trades, and let's say it is an extremely hinly traded stock, if there were 2 trades in the last 5 min, one at $26 and the last one at $90, the average would be 58. Upper limit would become 64. Yeah it should have been halted, at least in my understanding of how LULD should work.
 
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