Most Australian credit card providers have 44 or 55 day interest-free periods on purchases. This means that interest on the amounts you owe does not start to build up until the statement due date.
Interest-free periods often start on the first day of your billing cycle, not when you make a purchase. For example, if your credit card has an interest free period of 55 days, this means that you have 55 days from the day of your statement to pay the closing balance in full. After this period, the remaining balance will have interest charged on it.