Cristiano Ronaldo is now the world's highest paid athlete. He has also been accused of tax evasion. His team, Real Madrid, has rushed to his defense, saying that it has confidence that the star did nothing wrong and will be vindicated. But much has yet to unfold. Like fellow soccer star Lionel Messi--who was already convicted of tax fraud--Ronaldo's tax case is mostly about image rights and allegedly using shell companies to divert income away from tax authorities. In the case of both stellar athletes, these might sound like unique, multi-million dollar issues having nothing to teach regular-old taxpayers. Actually, though, there are surprisingly universal lessons in these cases.