A debt ceiling limit and overdraft on the government’s central bank account provide evidence in favour of the idea that monetary efflux occurs before reflux. These events occurred in Guyana, an economy with a managed exchange rate. While the exchange and inflation rates remained relatively stable during the period of overdraft, the central bank lost international reserves. It is argued that this outcome reflects some policy space under quasi monetary sovereignty. The events also raise the critical issue of debt sustainability, especially for economies without a hegemonic global currency. Therefore, MMT-type coordination of efflux and reflux is embedded in a stock-flow model of debt. The derived debt model includes the following characteristics: (i) the degree of coordination of efflux and reflux; (ii) the propensity to mop up excess reserves; and (iii) private sector’s expected demand for government securities.