Thanks for reaching out to us, emberlifestyle.

Updating a payee, class, and location from prior years of transactions will not affect the amount of your P&L. 

I added this link you can check: Customise reposts in QuickBooks Online. This will show you how to run reports and customize them to get the right data.

I'm willing to work with you and share some other details on processes and features in QuickBooks Online. Always here to help.