Money allows agents to achieve allocations that are not possible without it. However, currency in most economies is a uniform object, and there may be incentive compatible allocations that cannot be implemented with a uniform currency. We show that currency reform, ie, changing the monetary base by replacing one currency with another, is a powerful tool that can enable a monetary authority to achieve a desired allocation. Our monetary mechanism with currency reform is anonymous and features a nonlinear exchange rate between currencies and a monotone value of money. These results help interpret the characteristics of currency reforms observed in practice.