The answer to this question is subjective, as different countries have different tax systems and what may be considered "best" for one country may not be for another. However, some tax systems are considered to be more efficient, fair and effective than others.
The Nordic countries, such as Sweden, Norway, and Denmark, are often cited as having some of the best tax systems in the world. They have high tax rates, but they also have high levels of public services and welfare, which are paid for by the taxes. These countries have a relatively high standard of living and a relatively low level of poverty and income inequality.
The Netherlands, Switzerland and Canada are also recognized as having efficient and effective tax systems.
The best tax system is one that is efficient in collecting the revenue needed to fund government services, fair in its distribution of the tax burden and simple for taxpayers to comply with. It's also important for a tax system to be able to adapt to changing economic conditions, and to be flexible enough to accommodate different needs of different groups of citizens.
It's important to note that no tax system is perfect and each has its own advantages and disadvantages. It's also important to consider the cultural, political, and economic context of the country when evaluating a tax system.