If you have surprise ad-hoc taxes (i.e. laws) they you no longer have the rule of law. In this case it is almost an ex-post facto law as the tax applies to earn

If you have surprise ad-hoc taxes (i.e. laws) they you no longer have the rule of law. In this case it is almost an ex-post facto law as the tax applies to earnings that occurred before the tax existed. Surprise laws should bother you on general principles. Tax unpredictability, high taxes, or capping profitability is a great way to scare off businesses from operating in your jurisdiction.