International economic relation and trade are occurred in different currency system. The currency of one country may not be tendered in another country. So, the natural person or organization requires buying the currency of target country. In fact it is the process of converting one currency into another currency, which makes globalization and international trade possible. Buying and selling of currency is made in spot market, forward market, futures market, swap market, and option market. Additionally, change in real price, structural change, speculation, inflation, interest rate, public debt, and status of terms of trade make effect in equilibrium position of exchange rate. Yet, demand and supply of the currency determine appreciation and depreciation of currency. Policy exchange rate is accepted as fixed rate, floating rate, crawling band, crawling peg, conventional fixed peg arrangement, pegged exchange rate within horizontal band peg, currency board, dollarization and no separate legal tender. Earlier mint par theory was universally accepted. However, in contemporary time, balance of payment theory and purchasing power parity theory are accepted as theories of foreign exchange. Market transaction is made through hedging, speculation, and arbitrage etc. Exchange control is made through unilateral method and bilateral method. Unilateral method includes bank rate policy, import and export policy, exchange equalization fund, exchange pegging, multiple exchange rates, rationing of foreign exchange, and blocked account whereas bilateral method includes clearing agreement, payment agreement, installment agreement, differed payment agreement, and compensation agreement etc as per necessity. Nepal has accepted fixed peg exchange rate regime with Indian currency and flexible exchange rate regime with rest of the currencies
