I currently hold a stock trading on the ASX, and I noticed this morning that my sell order was automatically cancelled. Looking at the queues, I noticed that there were almost no orders in either buy or sell. Looking at the news artifacts for the company, I noticed that today is the ex-dividend date.
Why would buy and sell orders automatically be cancelled on ex-dividend date? Is it a courtesy extended by CHESS, in that an equity's price usually drops by an amount commensurate with the dividend?