Ann: 2017 Full Year Statutory Accounts and Appendix 4E, page-131

From commsec site.

Between 4:00 pm and 4:10 pm, Sydney time, the market is placed in Pre-CSPA. Trading stops and brokers enter, change and cancel orders in preparation for the market closing. The Closing Single Price Auction takes place between 4:10* pm and 4:12 pm, Sydney time. ASX Trade calculates closing prices during this phase.