When applying to register a trademark, you must select a "basis" for your application. Typically, your application is either "use based," meaning that you currently use the mark in commerce, or "intent-to-use," meaning that you do not currently use the mark in commerce, but have a good faith intent to do so in the near future. An intent-to-use application will undergo the same examination as a use-based application. The difference is, with an intent-to-use application, you must file a "Statement of Use" after the mark is approved in order for it to mature from an application into a registration.
You must file a Statement of Use within six (6) months of your mark being approved. However, you can file up to five (5) requests to extend the filing period for an additional six (6) months. Status Code 816 is triggered after you file a Statement of Use. It means that the the Examining Attorney has identified issues with the Statement of Use, and prepared an "Office Action" to you to explain what those issues are. You responded to amend the Statement of Use, but your amendment was not responsive to the issues identified by the Examining Attorney. For more information, see the notice you received from the USPTO. For information on the Trademark Application Process in general, visit:
For intent to use forms, visit:
For the USPTO's Intent-to-Use Application Timeline, visit: