Software for Invoicing System in Mexico

Hi, the project is about adding security features and modifying its functions in order to improve an existing Software. It was designed in PHP and Symfony with MySQL databases, and its communications in Java all set up in modules. The purpose of this software is to generate invoices under the government´s requirements for multiple users. The invoices are sent to a Certified Provider who certifies and stamps each invoice returning them to the software which saves it and automatically sends a copy to both: the sender and receiver of the invoice through email. The development is all set up on a web server Fedora 14 8gb RAM and 240 gb disk space physically located in the US. Its got to be developed other types of invoices with specific requirements, give the option to users to modify tax rates and add up other rates, add up customization tools, correct mistakes as well as add up options into features that users must have either already existing or not in the current software. it its also required modifications at the website in terms of information for users, documentation, links to social networks, and an online payment system. we look for someone who can certainly do all these and other changes the soonest considering that this tax obligation is about to apply to every single business within the country represnting the business oportunity expected. we are considering someone who can take care of the maintenance of the software and keep a business long term relation.