If you have sales that are missing, the chances are that you have some sales from a website or file import that are unrecognised. This is easy to check and rectify.
To fix this you will need to go to transaction audit, change the period to the relevant time frame, and click the “Unrecognised” button. Then you can select a transaction, right click on it and go to “Modify Identifier”. You can then change this to be the correct product by entering the correct barcode number or picking the product from the list.
Once changed, clicking the chain icon will attempt to reprocess all unrecognised sales. As long as the product is available in the location it was sold in, this will fix this sale. If the product is not available in the location that it has been sold in, duplicate the product to this location and then reprocess unrecognised sales using the chain icon.