For commission report, please go to Report, Invoice and use one between report#72 Commission by Commission Rate (with Invoice & C.M) and #76.Commission Report (with Invoice & C.M)
[Please make a note of the report name rather than report number since the report number may change in future.]
#75 Commission by Sales Rep (with Invoice & C.M) is most popular one since it gives you the subtotal per Sales Rep.
They have different format but almost same data except #75 Commission by Sales Rep (with Payment)
#75 calculates the commission based on the payment you received for your customer.
The other reports calculate the commission based on the invoice and credit memo.
Select the date range and Retrieve the report.
Sales Rep and Commission Rate information should be entered in Invoice screen in order to display any commission amount on the report.