developing countries Following Nicolas Kaldor's research, public finance in developing countries is strongly tied to state capacity and financial development. As state capacity develops, states not only increase the level of taxation but also the pattern of taxation. With the increase of larger tax bases and the diminish of the importance of trading tax, while income tax gains more importance. According to Tilly's argument, state capacity evolves as a response to the emergence of war. War is an incentive for states to raise taxes and strengthen states' capacity. Historically, many taxation breakthroughs took place during wartime. The introduction of income tax in Britain was due to the Napoleonic War in 1798. The US first introduced income tax during the Civil War. Taxation is constrained by the fiscal and legal capacities of a country. Fiscal and legal capacities also complement each other. A well-designed tax system can minimize efficiency loss and boost economic growth. With better compliance and better support to financial institutions and individual property, the government will be able to collect more tax. Although wealthier countries have higher tax revenue, economic growth does not always translate to higher tax revenue. For example, in India, increases in exemptions lead to the stagnation of income tax revenue at around 0.5% of GDP since 1986. Researchers for EPS PEAKS stated that the core purpose of taxation is revenue mobilization, providing resources for National Budgets, and forming an important part of macroeconomic management. They said economic theory has focused on the need to 'optimize' the system through balancing efficiency and equity, understanding the impacts on production, and consumption as well as distribution, redistribution, and welfare. They state that taxes and tax reliefs have also been used as a tool for behavioral change, to influence investment decisions, labor supply, consumption patterns, and positive and negative economic spill-overs (externalities), and ultimately, the promotion of economic growth and development. The tax system and its administration also play an important role in state-building and governance, as a principal form of 'social contract' between the state and citizens who can, as taxpayers, exert accountability on the state as a consequence. The researchers wrote that domestic revenue forms an important part of a developing country's public financing as it is more stable and predictable than Overseas Development Assistance and necessary for a country to be self-sufficient. They found that domestic revenue flows are, on average, already much larger than