If you want to calculate taxes by using your own tax engine or by integrating the
Billing TaxEngineAdapter Apex interface with a partner app, complete these
prerequisites.
Required Editions
Gather Tax Provider Details
If you want to use a tax service provider, gather this information:
- Tax provider’s seller code
- Tax provider’s mailing address
- Credentials for accessing the tax provider
Create a Named Credential
After you gather the tax provider details, create a named credential to secure and authenticate
API callouts to the tax engine.
Define a Custom Apex Adapter
If you use your own tax engine,
define a custom tax adapter by extending the TaxEngineAdapter Apex interface.
You can model your custom tax adapter’s implementation based on
this example.
From Summer ’25, Billing supports up to 2000
invoice lines for a single invoice. To avoid limit-related issues, test your TaxEngineAdapter
Apex interface’s implementation to make sure that it adheres to the Apex limit for total heap size.
