The aim of the paper is to assess the operations of the National Bank of Poland (NBP) in terms of their financial effects. The purpose is to calculate the financial costs and revenues resulting from day-to-day operations conducted by the Polish central bank and to indentify measures to make monetary policy less expensive. The research shows that profits from investing Polish currency reserves are smaller than the average costs of servicing foreign debt. Poland’s official reserve assets have strongly increased and exceeded a safe level in recent years. Excessive foreign reserves imply higher financial costs for monetary policy, mainly because of the need to absorb surplus liquidity from the banking sector. The conclusion is that the Polish central bank and Finance Ministry should modify and better coordinate their day-to-day operations. Poland’s currency reserves should be reduced by 30% to pay back a portion of the country’s foreign debt. That would help eliminate surplus liquidity in the banking sector without threatening the economy’s external balance or reducing the efficiency of monetary policy in achieving its final targets. As a result, the financial effectiveness of the central bank’s operations would improve.