a) If I pay income tax and e.g. war tax, then this is two taxes. b) If I pay income tax and then earnings tax on top of that, then it is double taxing. c) If I

a) If I pay income tax and e.g. war tax, then this is two taxes. b) If I pay income tax and then earnings tax on top of that, then it is double taxing. c) If I pay income tax to country A, then same tax to country B, then it is double taxing. We are talking about c). Wikipedia: Double taxation is the levying of tax by two or more jurisdictions on the same declared income (in the case of income taxes), asset (in the case of capital taxes), or financial transaction (in the case of sales taxes).