Hyperinflationary currency
(D) Hyperinflationary currency. For purposes of sections 985 through 989, the term hyperinflationary currency means the currency of a country in which there is cumulative inflation during the base period of at least 100 percent as determined by reference to the consumer price index of the country listed in the monthly issues of the International Financial Statistics or a successor publication of the International Monetary Fund. If a country's currency is not listed in the monthly issues of International Financial Statistics, a QBU may use any other reasonable method consistently applied for determining the country's consumer price index. Base period means, with respect to any taxable year, the thirty-six calendar months immediately preceding the first day of the current calendar year. For this purpose, the cumulative inflation rate for the base period is based on compounded inflation rates. Thus, if for 1991, 1992, and 1993, a country's annual inflation rates are 29 percent, 25 percent, and 30 percent, respectively, the cumulative inflation rate for the three-year base period is 110 percent [((1.29 1.25 1.3)1.0 1.10) 100 = 110%] and the currency of the country for the QBU's 1994 year is considered hyperinflationary. In making the determination whether a currency is hyperinflationary, the determination for purposes of United States generally accepted accounting principles may be used for income tax purposes provided the determination is based on criteria that is substantially similar to the rules previously set forth in this paragraph (b)(2)(ii)(D), the method of determination is applied consistently from year to year, and the same method is applied to all related persons as defined in 1.985-3(e)(2)(vi). (E) Change in functional currency when currency ceases to be hyperinflationary(1) In general. A QBU that has been required to use the dollar as its functional currency under paragraph (b)(2) of this section, or has elected to use the dollar as its functional currency under paragraph (b)(2)(ii)(B)(2) of this section or 1.985-2, must change its functional currency as of the first day of the first taxable year that follows three consecutive taxable years in which the currency of its economic environment, determined under paragraph (c)(2) of this section, is not a hyperinflationary currency. The functional currency of the QBU for such year shall be determined in accordance with paragraph (c) of this section. For purposes of 1.985-4, the change is considered to be made with the consent of the Commissioner. See 1.985-5 for adjustments that are required upon a change in functional currency.