I have driven in Western Europe and the US almost every year since 1989. I bought an IDP on the first trip and at that time nobody seemed interested so I ignored it until this year when I was advised by a travel agent that I needed it to drive in Spain. I checked the Government site and verified it. As with other's experience, the hire company wasn't interested but I did not have any interaction with the authorities so can't comment on that. What I can comment on is the extortion cost and limited life which I suspect it artificially enforced. It's also interesting that the Australian Government don't provide them but refer you to your association. Conclusion. It's a rort but I'll continue to "buy" one each year for insurance reasons from now on.