Indeed, some complex corporate structures may be used for tax planning, and some of them may involve improper or illegal behavior. Common strategies include： 1. Offshore structure: set up a holding company or subsidiary in a low-tax or tax-free area 2. Transfer pricing: Transfer profits between affiliated companies to low-tax areas through unfair prices 3. Complex structures such as "Double Ireland" and "Dutch Sandwich": taking advantage of tax treaties and legal loopholes in different countries 4. Shell company: establish a company without substantial operation to transfer funds It is worth noting that tax optimization itself can be legal, but it may be illegal when deliberately concealing information, providing false information, or establishing a structure with no substantial business purely for tax evasion. In recent years, the international community has strengthened the supervision and crackdown on such behaviors through measures such as the BEPS (tax base erosion and profit transfer) Action Plan and automatic information exchange.