"Core accounting software" is huge. Real-world systems are incredibly complex (GL, AP, AR, Payroll, Reporting, Auditing, Security, etc.). Providing all the code is impossible and impractical in a text-based format. The request specifies ASP.NET MVC with C#. This implies a web application structure. The goal should be to provide a foundational structure and illustrative examples of key accounting concepts implemented within this framework. This will give the user a starting point and demonstrate the principles. Chart of Accounts (CoA): Managing account definitions. Journal Entries (JE): Recording transactions (the core double-entry mechanism). Basic General Ledger View: Showing transactions grouped by account.