Effective income and wealth taxation is a central development cooperation issue because taxation of foreign companies and their own residents’ overseas assets remain problematic for developing countries. Estimates of the scale of undeclared expatriated profits and overseas assets, and thus the income tax lost to developing countries, are large relative to other forms of innovative development finance. The international cooperation required involves information exchange between jurisdictions to allow the full application of existing tax codes. This expanded global tax base would be a more sustainable and equitable system than the traditional donor-recipient relationship. 1. Introduction -- 2. Estimating the scale of tax revenue lost to developing countries -- 3. Institutional dimensions of international tax cooperation -- 4. International tax cooperation and international development cooperation -- 5. Drivers of Change -- 6. Conclusions.