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The Symmetry Tax Logic (STL) API is a single API endpoint that explains payroll tax calculations in plain language to employees. It transforms complex tax computation logic into clear, understandable explanations that employees can read and understand. The best part? You can implement it in a matter of minutes.

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What it does

The API has a single straightforward purpose: explain tax calculations in plain language for employees and payroll managers. Common use cases include:
  • Displaying tax explanations in employee self-service portals
  • Helping employees understand their paychecks
  • Supporting payroll inquiries and employee questions
  • Providing audit trails for tax calculation transparency
  • Helping payroll managers

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How it works

The API accepts a single request containing:
  • Your employee’s payroll calculation context (wages, deductions, jurisdictions)
  • The specific tax or taxes you want explained
The API returns a plain-language explanation of how that tax was calculated, ready to display to your employee.

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Integrate in three easy steps

A payroll calculation is performed in STE.
1

Retain the payroll context

Your application retains the STE payroll calculation log or JSON request (the payroll context).
2

Send the data to the STL API

You send that data to the STL API.
3

Display the explanation

The API returns a structured explanation and you display it in your UI.

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Who should use this

The Symmetry Tax Logic API is designed for Symmetry Tax Engine clients who want to provide transparent, understandable tax explanations to their employees. It’s particularly valuable for payroll platforms, HR systems, and employee self-service portals.

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Key features

  • Single endpoint: one API call to get explanations for one or multiple taxes
  • Plain language output: explanations are written for employees, not accountants
  • Context-aware: understands the full payroll context to explain how taxes were actually computed
  • Fast implementation: complete integration in one day using the included Developer Integration Kit
  • Multi-jurisdiction support: explains federal, state, and local taxes across all supported jurisdictions

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Get started and explore

Everything you need to implement, test, and support the STL API lives in the pages nested under this one:

Quick Start

The fastest way to get started — test with Postman, run a sample client, or dive into the full tutorial.

Full Workflow

A step-by-step walkthrough from authentication through displaying the explanation in your UI.

STL API Developer Integration Kit

A complete, self-contained toolkit with sample clients, AI-assisted guidance, and setup steps to integrate in about a day.

Payroll Context

How to capture and supply the complete payroll context the STL API needs to explain a tax.

PayCalc Session Recording

Capture, store, and replay STE calculation sessions — required for on-premise SDK clients.

Demo Video Library

Watch end-to-end demonstrations of implementing and using the STL API.

FAQs

Answers to common questions about testing, response behavior, context, and credentials.

Troubleshooting

Diagnose and resolve common issues when authenticating and calling the STL API.

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Payroll context

The STL API requires the complete payroll context for the employee’s paycheck — the same inputs provided to STE at calculation time. How you capture and supply it depends on your STE implementation: See Payroll Context for full details.

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Test the API

Explore and validate your integration using the Quick Start, which walks you through testing with the Postman collection and exploring the endpoints interactively with Swagger.

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Documentation and resources