Per IRS Publication 3112 IRS e-file Application and Participation, on page 14:

Registration of Websites with the IRS

To safeguard taxpayer information, the IRS requires Providers to register with the IRS all websites that collects taxpayer information, either directly or through third parties, and used by the Provider for federal returns that are filed electronically.

Providers must submit the below information to the IRS prior to the website being accessible on the Internet:

1. An EFIN for the Provider;
2. The name of a Principal or Responsible Official shown on the e-file application for the EFIN; and
3. The Uniform Resource Locators (URLs) of all websites from which the Provider collects information from taxpayers, either directly or through third parties, for electronic filing of federal returns.

Any changes to the information provided above must be made within three business days.

Providers must login to e-Services and navigate to the e-file Application. Click “URL Collection” and proceed as instructed. If “URL Collection” is not in the e-file Application Menu, click “Firm Information” and select“Yes” in response to the website question. After saving, the “URL Collection” link should be available on the “e-file Application” summary page.

Note that any link in the information above is updated each year automatically and will take you to the most recent version of the webpage or document at the time it is accessed.