billing software

A retail billing software which enables us to generate bills with the help of a bar code scanner. We will be using netbooks connected to a common printer. Software is required to be installed in these netbooks. Net books currently have linux based OS. The bill should show the VAT amount based on the VAT percentage entered while creating the bar code. The software should enable us to issue bills in our name. We have more than one establishment and so we should be able to change the name of establishment together our VAT no and sales tax approval number etc., Sales data (VAT % wise) as well as inventory reports should be available in Excel format. All formats of reports usually available in any billing software should be made available. Since VAT is a function of the Government, we should be able to change VAT whenever there is a change announced by the Govt. Source code of the software together with the finalised software is to be provided in 3 copies. Freelancer must provide email support for a period of 6 months atleast and 12 months if possible. If the coder is from Bangalore, we would request him / her to do the initial installation of software and provide support once a month for 6 months in person. Only freelancers from India are accepted. Software can be provided from any open source free billing software with due modification or as desired by the freelancer. Demo version incorporating all the above must be provided initially, which we will run for a period of one month, and due changes made to this version and total satisfaction essential before the final version is accepted. Regards