Tentatively, you need about three spreadsheets--one for trades, one for dividends/distributions, and one for interest.
For me, the latter two are similar, since you only need the amounts paid and the dates. On one sheet list the interest payments (likely x12), each with a date, and the payer (in my case) is the same for each, the name of my broker. For dividends, have columns for date paid, name of payer (ticker symbol), amount in dollars, then the TTM rate for that date, and the sheet then converts $ into yen for that. One row for each payment, total at the bottom (<-total is what you need to give when doing your return).
Trades (=sales) are a little harder, since you'll need two dates, and the TTM rates for both purchase date and sale date. The sheet will need to list amount for purchase and sale ($), and kind of like above, convert using the TTM for those dates into yen. So you'll then have a cost figure and a sale figure in yen.
For reporting on your return, you need the totals--cost of all trades totaled, and cost of all sales totaled. These are the figures required for input when doing the actual return. The system will then auto-calc the difference (gain/loss). I do the same on my spreadsheet, just as a confirmation of what's going on.
This may be your first year reporting this, and if so, you'll quickly see that it's a bit of book work--not hard, but it does take some time when doing a full year in one go. For this coming year, (2022) it will
really help to have these sheets started and updated thru the year, and you can do this with monthly statements, or what you see happening online. Since payouts are typically quarterly, April, July, and October might be good times. Then at the end (now) you'll only have a few more items to add.
Use
this site, often recommended for TTM rates (scroll down to the date dropdowns, don't use the calendars).
There's been discussion of this on the JapanFinance reddit sub, so maybe browse/search some over there, too.
