I wants a simple system in which you place products, customers and be able to issue invoices. That is like what is below with some changes that may occur
-Customers: contact details, prices they buying, terms of payment.
-Invoices: DROP DOWN LIST OF ALL CUSTOMERS, WHICH ALL WILL HAVE THE NEEDED DETAILS FOR INVOICE and I will insert the quantities.
- FOLDER for each customer: the invoices will move automatically to the folder. To show a statement of all the products they bought.
- Storage: I can add products to buy and automatically removed the products sold.