Bids to buy at a higher price are more likely to be successful than bids at a lower price.
Offers to sell at a lower price are more likely to be successful than offers at a higher price.
For bids or offers submitted at the same price, the bid or offer submitted earlier in the auction has priority, so is more likely to be successful.
Auto bids and auto offers are prioritised based on the limit orders that are submitted into the order book pursuant to the auto bid or auto offer. Auto bids and auto offers update their prices in the order they were submitted, so the first in time retains priority if bidding at the same price.
Updating existing orders
If you update an existing bid or offer, the time priority of that bid or offer will be reset (unless the only change is a reduction in the volume of a limit order and the limit price remains the same – in which case the order will maintain its original time priority).
Increasing existing orders
If you want to increase the size of an order at the same limit price without losing the time priority of your existing order, you can do this by submitting an additional order at the same price, for the incremental increase in volume, instead of amending your existing order. Make sure you select the option to submit an additional order rather than replacing your previous orders.