For taxable years after the final regulations are effective, taxpayers operating in hyperinflationary currencies must use the U.S. dollar as their functional currency and compute income using the dollar approximate separate transactions method (DASTM). Small taxpayers may elect an alternate method by which to compute income or loss. For prior taxable years in which income was computed using the profit and loss method, taxpayers may elect to recompute their income using DASTM.
The latest form for TD 8556 (Final) - Computation and Characterization of Income and Earnings and Profits Under the Dollar Approximate Separate Transactions Method of Accounting (DASTM) expires 2020-08-31 and can be found here.