Make sure you generate an API key before making any requests. See API Keys for details.

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Overview

The Numeral API allows you to calculate and collect sales tax for your business. With our API, you can:
  • Get tax information for products and addresses
  • Record completed sales
  • Handle refunds
  • Manage products and customers

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Authentication

All API endpoints are authenticated using Bearer tokens. Include your API key in the Authorization header of all requests: 
curl --request POST \
  --url https://api.numeralhq.com/tax/calculations \
  --header 'Authorization: Bearer YOUR_API_KEY' \
  --header 'Content-Type: application/json' \
  --data '{ ... }'

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Base URL

All API requests should be made to: 
https://api.numeralhq.com/

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API Versioning

The API is available in multiple versions:
  • 2024-09-01 (default) - Base functionality
  • 2025-05-12 - Enhanced with B2B support, tax IDs, automatic tax configuration, and more currencies
To specify an API version, include the X-API-Version header: 
--header 'X-API-Version: 2025-05-12'
If no version is specified, the default (2024-09-01) version is used. For details on version-specific features, see the individual endpoint documentation.