Update : Jan. 04, 2010
As explained in 'How is order priority decided?', orders are normally executed on the basis of price and time priority.
However, in the following circumstances orders are treated as simultaneous orders and time priority is ignored:
Note: All remaining orders from the morning session are treated as simultaneous orders at the beginning of the afternoon session.(Please 'What is a closing auction at the limit price?' for more details.)
These simultaneous orders are executed according to a mechanism determined by TSE as set out below.
Thus simultaneous orders are executed in proportion to the total amount of each Trading Participant's orders. Trading Participants then distribute the shares among their customers according to their own internal guidelines.