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Access to the Symmetry Tax Engine is licensed by Symmetry. How your license is delivered — and how you authenticate — depends on which interface you use.

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How you authenticate

Each interface uses one of three credentials. Use this table to find the one you need, then see the credentials below for details. * On-premise installs also use an API key for the Symmetry Location Service (address geocoding), separate from the STE license file.
For the hosted Web API and the hosted STE MCP, Symmetry runs the licensed engine on your behalf — you don’t manage a license file yourself.

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The credentials

STE license file

Authorizes the engine for an on-premise install; it’s part of the licensed distribution.

API key

A per-client/product key issued by Symmetry, sent as the raw value of the Authorization header on every request.

Client Support Center credentials

User-level sign-in — you authenticate as yourself, not with a shared service key.

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Hosted Web API

The STE Web API is accessed with an API key, included as an Authorization header on every request. You receive your keys when you sign, one per environment:
Use your staging API key only against the staging environment, and your production API key only against the production environment. Mixing them will cause your requests to fail.
Unsure of your API key? Open a support ticket and Symmetry’s Client Success team can help.

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On-Premise SDK

The On-Premise SDK is licensed with a license file named ste-license.dat, which you download from Symmetry’s Download Center (as a ZIP file with “License” in the name). Place ste-license.dat in your installation’s ste-root folder.
You must always include the license file as part of your distribution or installation. The Symmetry Tax Engine will not function without a valid license file.

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Location data and the Symmetry Location Service

Full street-address and geocoordinate geocoding uses the Symmetry Location Service (SLS). On the hosted Web API, SLS is handled for you. On an on-premise install, you set an SLS_API_KEY in ste.conf — a configuration detail, not a separate license.

Hosted API vs. On-Premise SDK

Decide which delivery model fits your needs.

Hosted API quickstart

Make your first authenticated request.

AI interfaces

Set up the STE MCP, Tax Logic Chat, and Tax Logic API.