I think something does force taxes to be complicated though and that is the fact that taxes are a useful tool of public policy and it is often one of the easies

I think something does force taxes to be complicated though and that is the fact that taxes are a useful tool of public policy and it is often one of the easiest ones to use. For example the federal government in the US can enact income and excise taxes to accomplish things that are otherwise outside the general powers of our federal government, such as heavily restricting machine gun ownership. I think as soon as taxes become a political tool, or a tool of public policy the question isn't whether they will become complicated but rather how complicated they will become. The floor here seems to me to be based on the willingness of the average voter to put up with the complexity vs the desire to see their public policy goals enacted. I think that these play out in two ways: 1) Local taxes tend towards less complexity than taxes which are national. 2) Taxes which everyone reports tend towards less complexity than taxes which few people report. Consider the current trends in state sales tax reporting vs trends in state income tax reporting...... There's no question that sales tax reporting on average is more complex now than income tax on a state level, and that its becoming more complex faster.