During the process of a business deal, you may have to provide an estimate for the cost of goods/services to the prospect customer. This can be done in a professional manner using GSSalesManager. During creation of estimate, stock does not get affected.
Notice the button "Convert To Invoice" at the bottom of the screen. This allows you to convert an estimate to Sale Invoice. Also you can amend it at any stage to suit your needs. The stock is updated only when the Estimate has been converted to Sale Invoice.