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What is Sales Tax as a Service? A white label tax compliance platform allows you to offer automated sales tax management to your clients. Your platform handles client onboarding, tax calculations, compliance tracking, and filing management—all powered by Kintsugi’s API.
Building a Sales Tax as a Service (STaaS) platform enables you to offer comprehensive tax compliance solutions to your clients without building the complex tax logic yourself. This guide series walks through building a complete white label tax compliance application using Kintsugi’s API.

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What You’ll Build

A complete STaaS platform includes:
  • Client Onboarding: Automated organization setup with business details, addresses, and banking information
  • Nexus Management: Track physical and economic nexus across jurisdictions
  • Registration Management: Automate tax registrations in states where clients have nexus
  • Product Catalog: Manage product tax classifications for accurate calculations
  • Transaction Processing: Calculate tax at checkout and sync completed transactions
  • Compliance Management: Track filings, approvals, and compliance status

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Integration Architecture

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API Endpoints Overview

A complete STaaS integration uses 19 distinct API endpoints across 5 phases:

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Phase 1: Organization Setup & Onboarding (8 endpoints)

Initial client setup endpoints:
  • Create organization
  • Generate API keys
  • Configure business details, addresses, contacts, owners
  • Set banking information

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Phase 2: Product Catalog Management (1 endpoint)

  • Create and manage products with tax classifications

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Phase 3: Nexus & Registration Management (3 endpoints)

  • Physical nexus creation
  • Economic nexus registrations
  • Registration status tracking

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Phase 4: Transaction Processing (4 endpoints)

  • Tax calculation
  • Transaction creation
  • Transaction retrieval

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Phase 5: Compliance & Filing Management (3 endpoints)

  • Filing list retrieval
  • Filing details
  • Filing approval

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Integration Patterns

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Choosing HTTP REST or SDK

All Kintsugi API endpoints are accessible via HTTP REST. The SDK is an optional wrapper that provides convenience methods and built-in error handling, but it calls the same REST API endpoints under the hood. You can use either approach:
  • HTTP REST: Direct API calls using your preferred HTTP client. Gives you full control over requests and responses.
  • SDK: Optional convenience wrapper around the REST API. Provides type safety, built-in pagination helpers, and simplified error handling.
Choose based on your preference:
  • Use HTTP REST if you prefer direct control, want to use your existing HTTP client, or are building in a language without an SDK
  • Use the SDK if you want convenience methods, type safety, and built-in helpers for pagination and error handling
Both approaches access the same API endpoints and provide the same functionality.

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Sequential Setup Pattern

Organization onboarding requires sequential API calls. Each step depends on the previous one:
  1. Create organization → Get organization_id
  2. Create API key → Get api_key
  3. Use both for all subsequent operations
Store credentials securely: The organization_id and api_key returned during onboarding must be stored securely in your database. These credentials are required for all subsequent API calls for that client.

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Complete Integration Workflow

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What’s Next?

This guide series is organized into 6 articles:
  1. Overview (this article) - Understanding the complete integration
  2. Organization Setup & Onboarding - Setting up new clients with 8 sequential API calls
  3. Nexus & Registration Management - Establishing tax presence and registrations
  4. Transaction Processing - Calculating tax and syncing transactions
  5. Product Catalog Management - Managing product tax classifications
  6. Compliance & Filing Management - Tracking and approving tax filings
Each guide includes:
  • Step-by-step instructions
  • Code examples
  • Mermaid diagrams showing data flow
  • Best practices and error handling
  • Integration patterns specific to STaaS platforms

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Prerequisites

Before starting, ensure you have:
  • Kintsugi Partner Account: Access to the Partners API
  • API Credentials: Your parent organization’s API key and organization ID
  • Development Environment: Ability to make HTTP REST calls (SDK is optional)
  • Database: Storage for client records, organization IDs, and API keys

Next: Organization Setup

Learn how to onboard new clients with 8 sequential API calls

API Reference

Explore the complete API documentation