The real problem behind your question lies in the low knowledge of a big percent of institutions in different countries that are appointed with the solving and managing the tax system. Financial experts, although they are not free, can be a great asset in a retrieving and convert the hard-earned crypto. Taxes are not avoidable and sooner or later if they are avoided you can be caught. There are solutions of retrieving the crypto without the tax system involved but that can be compared to the money laundry. If you have a big amount of convert financial accountant is needed solution for your transaction!