Why are tax systems so complex? What are the causes of tax law complexity? What are the consequences? Why is tax simplification so difficult to achieve? These, and related questions, lie at the core of this volume on tax simplification featuring chapters by leading tax experts around the world. The quest for simplicity è^' or at least some move towards simplification è^' has been a fixation of governments and others for many years, but little appears to have been achieved. Tax simplification is the most widely quoted but the least widely observed of the usually stated goals of policy (equity and efficiency being the others). It has been used (and abused) as a primary justification for tax reform over the last century, and typically it is seen as è^-a good thingè^-- è^' to say that one is in favour of tax simplification is tantamount to stating that one is in favour of good as opposed to evil.

Building on previous FAD work in the tax administration field, this paper defines broad criteria for diagnosing the problems in a country’s tax administration and formulating an appropriate reform strategy. To be effective, this strategy should be based on the size of the tax gap and the country’s particular circumstances. This paper discusses some guiding principles which have provided the basis for successful reforms, including: reducing the tax system’s complexity, encouraging taxpayers’ voluntary compliance, differentiating the treatment of taxpayers by their revenue potential, and ensuring the reform’s effective management. Also discussed are specific bottlenecks that hinder the effectiveness of the tax administration’s operations.

There is no consensus on how strongly the Tax Cuts and Jobs Act (TCJA) has stimulated U.S. private fixed investment. Some argue that the business tax provisions spurred investment by cutting the cost of capital. Others see the TCJA primarily as a windfall for shareholders. We find that U.S. business investment since 2017 has grown strongly compared to pre-TCJA forecasts and that the overriding factor driving it has been the strength of expected aggregate demand. Investment has, so far, fallen short of predictions based on the postwar relation with tax cuts. Model simulations and firm-level data suggest that much of this weaker response reflects a lower sensitivity of investment to tax policy changes in the current environment of greater corporate market power. Economic policy uncertainty in 2018 played a relatively small role in dampening investment growth.