What is the difference between the actual filing date and the effective filing date in pre-AIA patent law?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

In pre-AIA patent law, the actual filing date and the effective filing date can be different. The MPEP 2139.01 explains:

“The effective filing date of a claimed invention is determined on a claim-by-claim basis and not an application-by-application basis. It is possible for different claims in a single application to have different effective filing dates.”

The actual filing date is when the patent application is filed with the USPTO. The effective filing date, however, can be earlier if the application claims priority to a previous application. This distinction is important because:

• The actual filing date determines the expiration of the patent term.
• The effective filing date determines what qualifies as prior art against the claimed invention.

Understanding this difference is crucial for patent applicants and examiners in determining patentability and managing patent portfolios.