An auditor friend told me a story about a company that opened a subsidiary to do all their vehicle leasing for the company cars. By charging the main company only their costs, this subsidiary was able to show 0 profit, and so they avoided paying some higher tax rate on the cars they were leasing. (I've probably simplified the story to the point of nonsense, but that was the basic idea).

You can see why that sort of thing would be illegal and that kind of subsidiary would be legally required to charge the market rate for the services they were providing.