One of the key fundamentals of your business is working capital management. It is always a challenge to manage the cashflow component of your operations. There is plenty of market evidence that businesses of all sizes are struggling with having the cash resources to meet quarterly ATO payments, in particular the GST payments when they are due.
With the ATO stating on May 31st that they are moving from an "education" phase to an "enforcement" approach from July 2002, it means penalties for late payment! Why not develop a simple approach to having the cash resources when they are needed and have a "honey-pot" account for the GST liability when you receive your income.
Change your accounting & business processes to ensure that the GST component of the funds received are transferred immediately into a separate "honey-pot" account. Similarly, you can account for GST offsets from costs.
The Banks have competitive products to assist you with this simple change to business accounting and you will have the cash resources when needed and can avoid the "enforcement penalties" with the ATO and brand destroying tactics just to generate the needed cash!