Calculating tax on capital gains from a US mutual fund held for over a decade
I have several mutual funds that I've held for 10+ years in a US brokerage account. Until now, I've never sold any shares and have simply paid tax on dividends (four times a year) and capital gain redistributions (twice a year), all of which I have reinvested. This year I'm thinking of selling some shares. Am I correct in assuming that to calculate the Japanese tax, I would need to look up the exchange rate for every single investment I've ever made to each fund (the original purchase plus every reinvestment thereafter) and figure out all of the FX gains or losses over a span of 10+ years? Given that the reinvestments happened six times a year, this would be an insane amount of work to properly calculate everything. Is there any easier way to do this?