Long time ago, save money fiscally by taking it out was as simple as creating an account in an opaque country and get the money there. Many are observing, with different reactions, as that is finished. Countries are getting better at detecting the offender and technology also plays against them. It is easier to follow the money and holding cash is increasingly controlled nowadays. Also, very few countries are in a situation in which they want to disturb their neighbors not sharing tax data. Excessive amounts of cash can be the subject of an investigation, mobile phones may indicate a fictitious residence etc... Its very hard to avoid detection of the authorities and mandatory to have a great advisor. Even with that, disasters can happen.
That's why active residence options increasingly work with more efficiently and are more popular. At the end, its a way to save taxes and save us problems. There are still many tricks, but there are fewer everyday and long-term risk is greater. Many times, the countries take years to instruct a cause and years to resolve it. In the time that is being investigated, the offender may not be aware and increasingly dig his hole. I should also tell you one thing, goverments often are not fair nor rational, they can prosecute with dubious reasons, don't give them real reasons.
A trial with a goverments is a vital problem of the first order, it involves that the state will put all its machinery against us under laws that it controls; very bad situation. In addition, there may be situations where the same income end up being burden in two different states, since both are considered eligible because the income irregular situation. Savings in a moment of time can be more than repaid in the future. Beware of miraculous plans and uncontrollable risks.