Gross revenues are in the sales invoices tap. Assuming you use sales invoices only to record revenues.
There’s also the credit tap from which you get all your sales returns.
There’s also custom reports, but I’m not well experienced in it.
Who or what is the same? The customer is the same as the supplier, or the sales invoice amount is the same as the purchase invoice amount?
What do you mean by this? Are you referring to the sum of sales invoices and purchase invoices? Or are you referring to the balance due on individual invoices?
Minus what?
Please furnish more information on who is the customer, who is the supplier, what was sold, what was purchased, how much the transactions were for, etc. Illustrate your transactions by showing screen shots of the Edit screens.
I would suggest that you create a separate “offset” account (preferably in the balance sheet) where the matching debit notes and credit notes can be posted as contra entries.