RetireJapan

I am having a hard time understanding the way SBI computes 損益 and 取得単価.
I assume 取得単価 is the price when I purchased it, but the amount remains the same for all my TOPIX purchases regardless of date. SBI then computes my 損益 by comparing the current price with the 取得単価, so the variable is only the number of shares I purchased.

Are they averaging out my 取得単価. Would it not be clearer if they simply displayed the actual purchase price? Am I misunderstanding something?

I'm with Rakuten and mine shows the 平均取得単価 (Average purchase price) which makes more sense.

According to https://faq.sbisec.co.jp/faq_detail.html?id=11060, in a 特定口座, the 取得単価 is the Moving average price (移動平均価格) including fees. I'm not sure what they mean by moving average though. The 約定価格 is the actually purchase price and might be listed elsewhere. The 参考単価 is the Average purchase price (加重平均価格) but not sure how thats calculated.

How they calculate the 取得単価 is listed here https://faq.sbisec.co.jp/faq_detail.html?id=12226.
Roughly translated as:
Purchase price (約定単価) x No. of shares(株数) + fees inc. tax (手数料) = Delivery price (受渡精算金額)
Total delivery price (受渡精算金額) ÷ Total no. of shares (保有株数) = Moving average price (取得単価)

Basically, 取得単価 is going to be very close to the Average purchase price but not exact.

Wow thanks for spending time to research. I just wonder why they would post average purchase price as opposed to actual. I'd like to see how much I actually gained/lost from the specific transaction. Will try to look for the 受渡精算金額 thanks!

Probably completely wrong here, but could it be that when you come to sell the Topix, unless you sell only shares from one particular transaction then they would have to average out the buying price top calculate the gain anyway? In other words despite the separate transactions the purchases are all in one big pot and when you sell some it is difficult to specify that you want sell, say, 10 of the ones you bought on this day, and five of the ones you bought on that other day etc? You just sell some from whenever and the average purchase cost will be used to calculate the gain, maybe? Just a guess.

I know some foreign brokers allows you to specify which lots to sell but not sure of Japanese brokers.
I searched around but was not able to find any official information besides from Japanese forums.

According to them, if you have purchased the same stock at different prices/dates, when you sell them, the ones you bought first will be sold (FIFO - First In First Out). However, the capital gain will be calculated from the average purchase price (取得単価). I think it is possibly to make things easier for tax purposes and the 特定口座. I could be totally wrong of course.