Domain name registration should be considered a priority. Like any trade mark, logo, or brand name, your domain name is an integral part of your corporate identity. It should be something customers can recognise and associate with your business.
Australian domain names must abide by strict policy rules and are derived from your registered business name or product. As domain names are registered on a "first in, first served" basis, it is imperative to lock in your preferred Internet identity as soon as possible, even if you don't have a web site yet.
The same strict rules are not applied to the international .com domain names, if its available you can register it irrespective of your business name.
If you're starting a new business, it may be worthwhile checking the availability of the domain name you intend to use before deciding on your registered business name.