Navigate to the Sales > Sales List on the sidebar. This will present you with all the sales made arranged in a descending order.
Find the first column (Action column) in the table the click the Action button. If your display screen is small, then you will have to expand the row details by clicking the blue plus (+) icon to open the action column as shown in the image above. Click the Complement Sale link and confirm to complement the sale.
All complementary sales are pushed to the Products > Complementary Sales section and are recorded as business expenses.
Click Complementary Sales