This page explains the “Calculation and Display of Profit and Loss per Exchange” in cryptact.

We have received inquiries asking, "Can we calculate profit and loss for each exchange?" and "Can we upload files for each exchange and calculate profit and loss separately?"** Currently, calculating profit and loss for each exchange is not permitted. Please note that uploading files for each exchange and calculating them separately will yield completely incorrect results.**

This is because, according to the guidelines of the National Tax Agency, to calculate profit and loss for each exchange, it is necessary to upload all transactions at once and ensure there are no invalid transactions. Calculating results based on partial transaction uploads is meaningless.

For example, if you buy 1 BTC for 1 million yen on Exchange A and buy 1 BTC for 1.5 million yen on Exchange B the next day, the cost (average cost method) will be 1.25 million yen. If you then sell 1 BTC for 1.7 million yen on Exchange B, the realized profit will be 450,000 yen (= 1.7 million yen - 1.25 million yen). If you calculate transactions separately for Exchanges A and B, Exchange A will show zero profit and loss (since there was no sale on A), and Exchange B will show a realized profit of 200,000 yen (= 1.7 million yen - 1.5 million yen). The total will not match the original 450,000 yen. This discrepancy arises because you cannot calculate the cost of per BTC purchased at different exchanges without uploading all files. Therefore, do not upload transaction histories and calculate realized profit and loss separately for each exchange.