The bookkeeping exchange rate is generally based on the first foreign exchange benchmark exchange rate at the end of 1 month, which is also the exchange rate at the end of each month.

How to deal with it in financial software?

At the end of the month, because you use financial software, you only need to enter the benchmark exchange rate on the last day of the month in the settlement interface, and the system will automatically transfer foreign exchange to related subjects.

And when was the exchange gain and loss processing done?

Do it on the last day at the end of each month, that is, before the profit and loss carry-forward.

I hope I can help you!