One way to check your item set up is to run an item report and add columns to make it easy to check all your items are pointed at the right accounts on both sides as in both sales and purchases. This is often overlooked. Another is to run a report by clicking on the bottom line of your income statement to see a detailed listing of each category and check that there are debits where they are supposed to be and credits usually only in income accounts. I’ve seen item lists so poorly maintained that this report has debits in income and credits in expenses completely messing up the lines on the income statement. Understating sales and understating expenses is to be avoided.