WHILE ENTERING EXCHANGE RATE AND CHANGE DATE IN SALES TRANSACTION EXCHANGE RATE CHANGE AUTOMATICALLY

Let me share why the exchange rate changes automatically in QuickBooks Online, vijay-bhuva-trin.

You can enter your own exchange rate. However, QuickBooks will automatically change it since it's base the rates from the IHS Markit.

You have to re-enter the rate if you want to use it for the entire day. Please browse this link for more information: Enter and use your own exchange rates.

Don't hesitate to post again if you have follow-up questions about the exchange rate. I'll be right here to help you.