Vendor Activity History Report
The Vendor Activity History report shows every bill, payment, discount, and balance change for a chosen vendor over a date range. It includes a beginning-balance line so the report ties out to the vendor's outstanding amount at the start and end of the period.
Open it from {menu:vendor-activity-history|xaBPy9MShI}.

Running the Report
Pick the vendor and a date range, then generate the report to review that vendor's full activity and running balance.