There are basically two projects,
1. Create C#.NET CLass library with different WinForms (front end)
2. RESTful APIs (business logic)
.Net FW: 4.5.X
Database: SQL Server 2008
Here you have to create tables, sql procs, design forms and write code.
All business logic will go in RESTful web service, WinForms will almost have no logic and consume RESTful web service for data save/update/delete/query etc.
There are few our pre-build APIs, which provide data for Master-Lists. You have to call those where required and populate controls.
For detailed description, gothrough attached documents.
Full ownership of all code must be provided.
Do not use Third party controls.
To avoid automated bids, please mention answers too following questions in your bid
Q1. Total How many forms are there to develop ?
Q2. Which Payment API you have to integrate ?
Q3. Is there any Access Control / Permission based system ?