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Tax consequences when foreign currency changes in value
If you buy foreign currency as an investment, then the gains are ordinary income. The gains are realized when you close the position, and whether you buy something else go back to the original form of investment is of no consequence. In case #1 you have $125 income. In case #2 you have $125 income. In case #3 you have $166 loss. You report all these items on your Schedule D. Make sure to calculate the tax correctly, since the tax is not capital gains tax but rather ordinary income at marginal rates. Changes in foreign exchange between a transaction and the conversion of the proceeds to USD are generally not considered as income (i.e.: You sold a property in Mexico, but since the money took a couple of days to clear, the exchange rate changed and you got $2K more/less than you would based on the exchange rate on the day of the transaction - this is not a taxable income/loss). This is covered by the IRC Sec. 988. There are additional rules for contracts on foreign currency, TTM rules, etc. Better talk to a licensed tax adviser (EA/CPA licensed in your State) for anything other than trivial.