The negative relationship between tax rates and FDI is well known. This paper looks at how complexity of the tax system affects FDI. Fulfilling tax requirements can be time-consuming, and this implies a cost for more complex tax systems. Alternatively, complexity may provide opportunities to reduce the overall tax bill. We find that measures of tax complexity have a significant inhibiting effect on the presence of FDI for a country pair, but have little impact on the level of FDI flows. A 10% reduction in tax complexity is comparable to a one percentage point reduction in effective corporate tax rates.