Not if you paid for the stuff in Euros. But if you changed the appreciated Euros back into dollars, you’d at least theoretically owe tax on a foreign exchange

Not if you paid for the stuff in Euros. But if you changed the appreciated Euros back into dollars, you’d at least theoretically owe tax on a foreign exchange gain. For pocket money, no one is going to bother with it. But I’ve been in situations involving hundreds of thousands of dollars held for long periods in foreign currencies, where the tax consequences were real. There’s a line on the 1040 to account for foreign exchange gain/loss.