In this book, I characterize conditions under which optimal monetary and fiscal policy is time consistent in a stylized small open economy with a flexible foreign exchange rate regime. I show that these conditions depend on the way in which leisure is assumed to enter preferences and/or on the process which productivity is assumed to follow. I further argue that these conditions will fail to be sufficient if the small open economy implements a fixed foreign exchange rate regime. Thus, in a small open economy with conventional debt instruments and with households who have preference over consumption, leisure, and real money balances, it is impossible to have the following at the same time: perfect capital mobility, a credible fixed exchange rate, and time consistency of optimal fiscal policy. Finally, I discuss how to understand the long-term stability of monetary unions from the time-consistency perspective.