There are a multitude of information returns that United States taxpayers may need to file if they own foreign assets or have foreign investments. Two of these forms are the FBAR (Foreign Bank Account Report) and Form 8938 (Statement of Specified Foreign Financial Assets). When a taxpayer is obligated to file one of these forms, the instructions require such taxpayer to report the value of the foreign investment in USD, which requires converting the foreign currency.
The FBAR instructions and those for Form 8938 advise taxpayers to use the Treasury's Financial Management Service rate found at www.fms.treas.gov from the last day of the calendar year. At times it can be difficult to find this rate. However, the December 31, 2013 rates were recently posted at http://www.fms.treas.gov/intn.html#rates. Furthermore, for taxpayers filing delinquent or amended returns, historical rates can now be found at http://www.irs.gov/Businesses/Small-Businesses-&-Self-Employed/Treasury-Department-End-of-Year-Exchange-Rates.