Short Term Trading Week Starting: 5 Mar, page-92

Well my understanding is this a broker will look to fill the order from one of their own clients first. Failing that they will Goto asx or chi-x to get a fill if a matching is buy is available. If not you remain at top of queue. So assume I sell order for XYZ at 60000 @10c and my order is at top of sell queue. Let say my broker has a buy for 50k at the same price. So there is match and 50k gets sold without going to asx or chi-x and broker saves on fees this way. Now each broker will also do the same and match internally if possible. This is why it is possible for someone behind you in the queue to get a fill before you. Annoying but the way it is unfortunately. The only solution is to either wait till a buyer steps up to your price and is not filled pre asx chi-x or lower your sell price to meet the market.