The Japanese tax system applies relatively low marginal tax rates on most economic activities which, in combination with moderate tax elasticities of the bases, indicate that the overall distortion from the tax system (the excess burden) is probably modest compared with other OECD countries. Recent sizeable reductions in statutory marginal tax rates in both the personal and the corporate tax system have strengthened this feature. However, significant loopholes and non-neutralities are in place in key parts of the tax system, leading to potentially substantial efficiency losses once the tax-to-GDP ratio starts rising to accommodate the restoration of public finances as well as the expenditure needs related to the ageing population. There is thus an immediate need to start broadening the tax base in major parts of the system, including reducing the vast allowances and credits in the personal income tax system; incorporating bonuses in the base for social security ...