Build Accounts Receivable Module

I’m extending our existing web-based application to cover the full accounts-receivable cycle. The new module must sit inside the current web app, so please plan your code to use the same tech stack, database, and authentication flow that is already in place... (Budget: $30 - $250 USD, Jobs: .NET, Accounting, API, API Development, ASP.NET, Database Management, HTML, PHP, Software Development, Web Development)