Building an E-Invoicing System (Webbased, MobileApp)

We need to develop an E-invoicing system where we have some requirements to generate the invoice according to the regulatory body. There will be three main entities, Users, Customers, Products, Invoices. The interface should be composed of a main Dashboard, reports, management pages for the main entities. The interface should also have option to change UI color-scheme based on user preference along with the Logo on top left corner. The same would be applied to the Mobile App as well.