InvoiceKit is a modern, open source .NET SDK for generating professional PDF invoices with support for custom themes, invoice line items, totals, due date calculations, and more.

🚧 This project is in early development.

Expect breaking changes, limited functionality, and rapid iteration as the core features are built out.

• 📄 PDF Export – Generate professional PDF invoices programmatically.
• 🎨 Theme Support – Easily swap between themes (classic, modern, contemporary) or define your own.
• ⚙️ SDK for .NET – Clean, fluent API designed for integration into any C# or .NET application.
• 🧾 Invoice Structure – Supports line items, subtotal/tax/total calculations, due dates, and notes.

var invoice = new InvoiceBuilder()
    .WithCompany("IT Services LLC")
    .WithClient("ACME,  Inc.")
    .AddItem("Widget", item => item
        .WithQuantity(2)
        .WithPricePerUnit(29.99m))
    .WithStandardTerms(days: 30)
    .Build();

invoice.SaveAsPdf("invoice.pdf");

• Build PDF rendering engine
  • Enhance PDF rendering blocks with fluent-API
  • Enhance multi-page support
• Define core domain models (Invoice, Line Items, Customer) w/ unit tests
• Create SDK fluent API
• Documentation
• Publish SDK on NuGet

Nice to have:

• Figure out PDF unit test strategy
• Add theme support with built-in defaults:
  • Contemporary
  • Modern
  • Classic
• Custom unit formatters and localization

MIT License

💡 Open Source Commitment

InvoiceKit is and always will be open source. This project is built with the developer community in mind. That includes a committment to maintaining InvoiceKit as a free and open source software.