ATO has tax-filing software that only runs on that other OS. MacOS and GNU/Linux users are out of luck but the ATO will allow them to deduct from taxes the cost of running that other OS just to run the software, a pure subsidy of M$.
STUPID! STUPID! STUPID! Australians and their government do not owe M$ a living. M$ should work for a living and Australian taxes should not go directly into M$’s coffers. Make your software a web-application that any browser on any OS can access. Get your act together, ATO.