RE: Sells16 Sep 2021 16:53
Smallfry, it works differently between LSE and ASX.
LSE decide upon buy and sell using the theoretical mid point of the spread compared to the 'theoretical price of the trade".
I'll return to theoretical bit, but, in essence, they compare the trade price with the mid point , low is taken to be a sell , high a buy , matching is unknown!
Theoretical is down to trades on LSE being treated as a single transaction against a single spread, whilst part-fills can be at varying prices and once the lowest price is exhausted, the spread will rise accordingly.
LSE probably use the weighted-average as the trade price.
ASX treat part fills as individual transactions in determining buy/sell status!
So one trade can be reflected as a mixture of buys and sells, with the lowest price rising in parallel with the low end of the spread. The closing price in ASX is the value of the final trade (or part fill), whilst LSE use the average of the spread or the last Uncrossing Trade which is often outside the spread?
Weighted average?
Say 500 shares are available at 2.3p , 800 @ 2.4p and 2500 @ 2.5p with loads more at higher prices. Also, say you want to buy 3000 shares at a limit of 2.6p!
The cost is actually 500@2.3 + 800@2.4 + 1700@2.5 (totalling 7320p) , and leaving 800 free @2.5p - the new low end of the spread!
The WEIGHTED average is 7320p / 3000 or 2.44p less than the mid point of the defunct spread 2.3p upwards? And spread is now temporarily 2.5p upwards.
Hope that makes it clearer Smallfry.
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I am a happy bunny!