You must express the amounts you report on your U.S. tax return in U.S. dollars. If you receive all or part of your income or pay some or all of your expenses in foreign currency, you must translate the foreign currency into U.S. dollars. How you do this depends on your functional currency. Your functional currency generally is the U.S. dollar unless you are required to use the currency of a foreign country.
Use the exchange rate prevailing when you receive, pay, or accrue the item. If there is more than one exchange rate, use the one that most properly reflects your income. You can generally get exchange rates from banks and U.S. Embassies.
the decline in value of your investment may be deductible when you liquidate it.
