Application Program Interface (API)
Issuers of Annual Tax Documents
Your company sponsors (or engages another company to sponsor) a server that hosts annual tax document data and interfaces with tax software applications.
Data Hosting Service for Annual Tax Documents
A company engaged to host annual tax document data that interfaces with tax software applications.
Income Tax Return Preparation Applications
Your tax software retrieves tax document data on behalf of a taxpayer from an API server and imports the data into the tax return of the taxpayer.
For implementation details see FDX REST API