The Australian Competition and Consumer Commission has instituted proceedings against the major petrol retailers in Australia and a petrol pricing information service, Informed Sources. For several years the petrol retailers have all contributed their retail price information to Informed Sources and received information in relation to all retailers pricing within half an hour of price adjustments. The ACCC alleges that the arrangement is an anti-competitive agreement in contravention of section 45 of the Competition and Consumer Act (the general prohibition on anti-competitive agreements). The ACCC alleges that the arrangement facilitates coordination between the petrol retailers through their ability to test proposed price increases in near real time and withdraw or sustain those price movements depending upon the reaction of competitors. The ACCC will argue that overtime the retailers observe patterns of conduct that support a tacit understanding as to price increases leading to a decrease in competitive rivalry. The proceedings follow a lengthy investigation by the ACCC and the ACCC having publicly expressed concerns regarding the Informed Sources business model. The case is significant as it is the first major enforcement proceedings to be brought by the ACCC in relation to information sharing by competitors where that information sharing falls short of cartel conduct. The ACCC is likely to face challenges in its case as it is unclear what evidence may be available to establish a counterfactual in which competitive rivalry would be greater or prices would be lower.