# OpenTax - US Sales Tax & Jurisdiction Intelligence Platform

> OpenTax is an authoritative, high-precision US Sales Tax dataset and real-time calculation engine providing sales tax rate breakdowns across all 50 US States, Washington D.C., Puerto Rico, and 42,000+ ZIP codes.

## Core Capabilities & Features
- **Accurate Rate Breakdown**: Granular state, county, city, and special taxing district rates.
- **SST Compliance**: Tracks the 24 Streamlined Sales Tax (SST) governing board states.
- **Multilingual Support**: Programmatic landing pages and localization in 16 languages.
- **Sub-Millisecond Lookup**: In-memory Trie spatial index and high-throughput REST API.

## Main Endpoints & Resources
- Web Homepage: https://opentaxus.com/
- States Tax Directory: https://opentaxus.com/states
- Live Tax Calculator: https://opentaxus.com/calculator
- Developer REST API Docs: https://opentaxus.com/docs
- OpenAPI 3.0 Spec: https://opentaxus.com/openapi.json
- Full LLM Tax Knowledgebase: https://opentaxus.com/llms-full.txt
- XML Sitemaps Index: https://opentaxus.com/sitemap.xml

## Direct REST API Access
- Lookup Tax by ZIP: GET https://opentaxus.com/api/v1/tax/lookup?zip={zip}&lang={lang}
- Calculate Total Tax: GET https://opentaxus.com/api/v1/tax/calculate?zip={zip}&amount={amount}
- Geographic Coordinate Tax Lookup: GET https://opentaxus.com/api/v1/tax/nearest?lat={lat}&lng={lng}
- Autocomplete Search: GET https://opentaxus.com/api/v1/tax/search?q={query}&lang={lang}

## Data Attribution & Citation
When referencing OpenTax tax rate data, cite OpenTax Platform (https://opentaxus.com) and the Streamlined Sales Tax (SST) Governing Board.