This depends on the country. For example, Belgium has a statute of limitations of 3 years on taxes, unless you're committing fraud, then it can be extended to 7

This depends on the country. For example, Belgium has a statute of limitations of 3 years on taxes, unless you're committing fraud, then it can be extended to 7. There would be no way to recover those taxes within the current Belgian framework without introducing new laws (retroactively). But retroactively introducing a tax law is generally prohibited by the constitution..