The Austrian VAT Calculator API is a RESTful service designed to calculate VAT (Value Added Tax) for Austrian purchases based on net, gross, or VAT amounts. The API supports multiple VAT rates commonly used in Austria (10%, 13%, and 20%) and follows best practices such as API versioning, testing, and dependency injection.

• .NET 8: Built with the latest .NET 8 framework.
• API Versioning: Future-proof API structure with URL-based or header-based versioning to support multiple versions.
• Swagger Documentation: Integrated Swagger UI for API exploration and testing directly in your browser.
• Docker Support: Dockerfile included for containerization and deployment in any environment.
• Unit and Integration Tests: Comprehensive test coverage to ensure the reliability of the application.
• FluentValidator: Used for validating input requests, ensuring data integrity and preventing invalid operations.
• Central Package Manager: Leverages .NET’s Central Package Management to streamline NuGet dependency management.
• GitHub Actions: Automated CI pipeline for building and testing the application.

• .NET 8 SDK
• Docker (optional)

1. Clone the repository.

git clone https://github.com/dianper/vat-calculator-api.git
cd vat-calculator-api

2. Restore NuGet packages.

dotnet restore

3. Build the project.

dotnet build

To run the application locally, follow these steps:

1. Run the API.

dotnet run --project src/Presentation.API/Presentation.API.csproj

2. Access Swagger UI: Open your browser and go to http://localhost:5000/swagger/index.html. This page provides a UI to interact with the API and view its documentation.
3. API Versioning: The API supports versioning in the URL. Example: http://localhost:5000/api/v1/vat/calculate

To run the application in a Docker container, follow these steps:

docker-compose up --build

1. Access Swagger UI: Open your browser and go to http://localhost:5000/swagger/index.html.

The API provides endpoints to calculate VAT based on either the net amount, gross amount, or VAT amount.

• POST /api/v1/vat
• Request Body: VATRequest

{
  "net": 100.0,
  "vatRate": 0.20
}

• Response: VATResponse

{
  "net": 100.0,
  "gross": 120.0,
  "vat": 20.0,
  "isValid": true,
  "message": "VAT calculation successful."
}

The API returns detailed error messages in case of:

• Missing or invalid input (non-numeric values, zero amounts)
• Invalid VAT rate (other than 10%, 13%, or 20%)
• More than one input type provided (e.g., net and gross)

This project includes both unit and integration tests.

dotnet test --filter UnitTests

dotnet test --filter IntegrationTests

These tests ensure that the VAT calculations and API behavior function as expected.

This API is inspired by the VAT calculations available on Calkoo VAT Calculator. It has been adapted to meet Austrian VAT requirements.