The deductibility of provincial business taxes in a federation with vertical fiscal externalities

Should provincial business taxes be deductible under a federal profit tax? We show that the 'optimal deductible,' which neutralizes the vertical fiscal externality between the federal and provincial government, is the change in the federal tax base per dollar of tax revenue collected by the provincial government. The optimal payroll tax deductibility rate depends on the extent to which it is shifted to workers and on the difference between the federal tax rates on profits and on labour income. Two apparently contradictory positions-full deductibility of a payroll tax and non-deductibility - are special cases of our model.