Currency Conversion to Yen for Japanese Taxes

[Nattokin]

I'm aware of Japanese Tax Law Article 57-3 《Conversion of Foreign Currency Transactions》https://www.nta.go.jp/law/tsutatsu/kiho ... 11a/01.htm, and of the need to use daily TTM rates for converting things to JPY. However, for transactions from many years past for which I now have no way of knowing the specific dates of transaction, does anyone know if it's possible to use an annual average US$ to JPY exchange rate -- similar to the annual exchange rates allowed by the IRS for US tax reporting https://www.federalreserve.gov/releases ... efault.htm?

If so, where can I find Japanese NTA-approved US$ to JPY annual exchange rates for years past?

I've got an old US deferred-tax retirement account that had quarterly gains over the years, but my only documentation is old year-end statements that simply show the yearly total gains.

And if I can't use an annual rate, any thoughts on what I should do?

[captainspoke]

This goes to 1990, so might go partway (use the dropdowns below the calendars). This site was suggested to me by the NTA:

https://www.murc-kawasesouba.jp/fx/past_3month.php

It might help to say just how far back you need to go.

[YouMeWeThem]

I've seen starkimpossibility on reddit suggest that the NTA may be flexible in these cases where accurate reporting is not possible, assuming you can make the case that you're not underpaying. For example if the unknown values are from 1990 to 1995, they may accept taking the maximum TTM in that time range and applying that to the total value of those funds. Obviously you'd want to talk with the people at your local tax office.

Also, you're explicitly allowed to claim the cost basis as 5% of the sale price if the cost basis is unknown - https://www.nta.go.jp/taxes/shiraberu/t ... o/3258.htm

[Nattokin]

Thanks both of you. This gives me something to go on.
Incidentally, that Mitsubishi UFJ site is the one I've been using for daily TTM rates, but I'd never paid attention to the average 平均 tab before.

[Nattokin]

Follow-up

I just compared the Mitsubishi UFJ annual midrange rates and the US Fed yearly exchange rates for 2020 through 2023 (links given above), and I found their annual rates were essentially the same:

2020 2021 2022 2023
106.82 109.80 131.43 140.56 Mitsubishi UFJ
106.78 109.84 131.46 140.50 US Fed

[captainspoke]

Maybe not, but you seem to be gravitating towards using an average. If you have truly exhausted not being able to find the rate for a pre-1990 date, okay, But until then, using an average for that year may not be acceptable.

This is what I got when I simply googled for the USD/JPY exchange rate for July 1, 1985.

https://www.poundsterlinglive.com/bank- ... o-JPY-1985

And that supposedly goes back to '75. Do you need anything farther back than that?

[Beaglehound]

Maybe not, but you seem to be gravitating towards using an average. If you have truly exhausted not being able to find the rate for a pre-1990 date, okay, But until then, using an average for that year may not be acceptable.

This is what I got when I simply googled for the USD/JPY exchange rate for July 1, 1985.

https://www.poundsterlinglive.com/bank- ... o-JPY-1985

And that supposedly goes back to '75. Do you need anything farther back than that?

I think the issue is the OP doesn't know the actual dates of transactions.

[captainspoke]

Okay, got it -- sorry.

(tho re-reading the initial post, needing to find exchange rates is prominent... so maybe both?)

[Nattokin]

Thank you. This other site info could be helpful, as well.

All I know is the years -- not specific dates within those years.

Since I only have year-end financial statements dated 12/31 that show the yearly totals, I supposed another approach would be to treat the transactions as carried out on 12/31 and use the rates for 12/31 each year.

Anyway, I'll collect everything I can, and then I'll run it all past the local tax office people for their opinion on what to do and what exchange rates to use.

Again, thanks!