I’ve added additional details to my invention/idea but I’ve already filed for patent. Can I modify my patent application after I’ve already filed it?

A very common question indeed. The break down is quite easy to understand when following this logic:

 

ADDING NEW SUBJECT MATTER

1. Any Patent-Pending Application, whether it is Provisional or Non-Provisional, cannot be modified to include additional details (referred to as “New Subject Matter”) after its filing date.
2. To add New Subject Matter to any pending application (referred to as the “priority application”), an additional patent application for the New Subject Matter must be filed before the priority application is granted or expires.  
3. The additional patent application is known as a CIP Application.

CIP EXAMINATION

1. The CIP Application, in its documentation, establishes a priority claim to the previously pending patent application to which the new subject matter relates.
2. The CIP Application receives a separate patent examination from the priority application.
3. During Examination, New Subject Matter receives a patent priority date even with the date of CIP filing while the Subject Matter Included in the Priority Application retains its earlier patent priority date.

CIP TIMING

1. Therefore, the timing of the CIP filing is important.  It should occur as soon as the new subject matter is conceived and the value of the subject matter is confirmed for patent filing.
2. The CIP Application can be filed as either provisional (informally) or non-provisional application. However, filing a CIP as a provisional is only recommended if its priority application is also a provisional AND the applicant is still not prepared to convert the provisional patent application to a non-provisional patent application.

If you are interested in more detail related to your situation it is best to speak with an attorney.

 

Source: Smartup Legal