> ## Documentation Index
> Fetch the complete documentation index at: https://docs.symmetry.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Symmetry Tax Logic API

> A single API endpoint that explains payroll tax calculations in plain language for employees and payroll managers — implementable in a day.

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.

## 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

## 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.

### Integrate in three easy steps

A payroll calculation is performed in STE.

<Steps>
  <Step title="Retain the payroll context">
    Your application retains the STE payroll calculation log or JSON request (the payroll context).
  </Step>

  <Step title="Send the data to the STL API">
    You send that data to the STL API.
  </Step>

  <Step title="Display the explanation">
    The API returns a structured explanation and you display it in your UI.
  </Step>
</Steps>

## 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.

## 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](/ste/ai-interfaces/tax-logic-api/developer-integration-kit)
* **Multi-jurisdiction support**: explains federal, state, and local taxes across all supported jurisdictions

## Get started and explore

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

<CardGroup cols={2}>
  <Card title="Quick Start" icon="rocket" href="/ste/ai-interfaces/tax-logic-api/quick-start">
    The fastest way to get started — test with Postman, run a sample client, or dive into the full tutorial.
  </Card>

  <Card title="Full Workflow" icon="list-check" href="/ste/ai-interfaces/tax-logic-api/full-workflow">
    A step-by-step walkthrough from authentication through displaying the explanation in your UI.
  </Card>

  <Card title="STL API Developer Integration Kit" icon="toolbox" href="/ste/ai-interfaces/tax-logic-api/developer-integration-kit">
    A complete, self-contained toolkit with sample clients, AI-assisted guidance, and setup steps to integrate in about a day.
  </Card>

  <Card title="Payroll Context" icon="file-lines" href="/ste/ai-interfaces/tax-logic-api/payroll-context">
    How to capture and supply the complete payroll context the STL API needs to explain a tax.
  </Card>

  <Card title="PayCalc Session Recording" icon="record-vinyl" href="/ste/ai-interfaces/tax-logic-api/paycalc-session-recording">
    Capture, store, and replay STE calculation sessions — required for on-premise SDK clients.
  </Card>

  <Card title="Demo Video Library" icon="clapperboard" href="/ste/ai-interfaces/tax-logic-api/demo-video-library">
    Watch end-to-end demonstrations of implementing and using the STL API.
  </Card>

  <Card title="FAQs" icon="circle-question" href="/ste/ai-interfaces/tax-logic-api/faqs">
    Answers to common questions about testing, response behavior, context, and credentials.
  </Card>

  <Card title="Troubleshooting" icon="wrench" href="/ste/ai-interfaces/tax-logic-api/troubleshooting">
    Diagnose and resolve common issues when authenticating and calling the STL API.
  </Card>
</CardGroup>

## 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:

* **STE JSON API**: capture and save the flat employee `payCalc` object.
* **On-premise SDK**: enable [PayCalc Session Recording](/ste/ai-interfaces/tax-logic-api/paycalc-session-recording).

See [Payroll Context](/ste/ai-interfaces/tax-logic-api/payroll-context) for full details.

## Test the API

Explore and validate your integration using the [Quick Start](/ste/ai-interfaces/tax-logic-api/quick-start), which walks you through testing with the Postman collection and exploring the endpoints interactively with [Swagger](https://api.symmetry.com/tla/docs).

## Documentation and resources

* [Quick Start](/ste/ai-interfaces/tax-logic-api/quick-start): the fastest way to get started.
* [Full Workflow](/ste/ai-interfaces/tax-logic-api/full-workflow): a step-by-step walkthrough from authentication through UI display.
* [STL API Developer Integration Kit](/ste/ai-interfaces/tax-logic-api/developer-integration-kit): download the complete toolkit and get started in minutes.
* [Payroll Context](/ste/ai-interfaces/tax-logic-api/payroll-context)
* [PayCalc Session Recording](/ste/ai-interfaces/tax-logic-api/paycalc-session-recording)
* [STL API Demo Video Library](/ste/ai-interfaces/tax-logic-api/demo-video-library)
* [STL API Frequently Asked Questions (FAQs)](/ste/ai-interfaces/tax-logic-api/faqs)
* [STL API Troubleshooting](/ste/ai-interfaces/tax-logic-api/troubleshooting)
* [Full API Reference (Swagger)](https://api.symmetry.com/tla/docs)
* [Error and Status Codes](/ste/reference/error-and-status-codes)