What is an effective filing date?

What is an effective filing date?

If you”ve done some reading about patents, you may have seen references to an “effective filing date.” For instance, while patent attorneys will often shorthand an explanation of patents by saying they offer protection for twenty years from filing date, they really mean that patents last twenty years from their effective filing date.

Typically, for most patent applications, the effective filing date is the day the application was filed. However, not all patent applications are typical; they can be continuations, continuations-in-part, or divisionals. While these can all issue as patents, they have special significance (a divisional, for instance, is an application that splits off from an original patent application, because the original claimed two or more inventions when it can only legally claim one) and they don’t always use their own filing date as the effective filing dates.

Instead, effective filing dates adopt the filing date of the application from which they sprung. So if the original – or parent – application was filed on January 1, 2009, and a divisional was filed on May 1, 2010, that was originated from the parent application, the divisional’s effective filing date will be January 1, 2009.

If you first file a provisional application and then later file a non-provisional, that non-provisional application can claim the provisional’s filing date as its own. The provisional’s filing date becomes the effective filing date for the non-provisional application and the patent that eventually issues.

These domestic examples are not the only situations in which a filing date is significant.  If your US application claims the benefit of an earlier foreign filing, the foreign filing date is not applied to your US application, but it can be relied upon for some prior art rejections.

What are the ramifications of effective filing dates? There are many. First, most patent applications are published 18 months after their effective filing date. Thus, in the example above, the parent and its divisional child will both be published on June 1, 2010. That means the divisional will be published just one month after it was actually filed. Publication day can be a starting point for obtaining damages in the event of infringement. Also, an earlier filing date can be an obstacle for other patents. Because the filing date is the presumptive invention date, an earlier effective filing date can mean that patent applications filed later by others can be refused because they were presumably invented later than yours.  And lastly, the filing date is the date on which an invention is deemed to have been invented for prior art purposes.  Thus, references that post-date the effective filing date cannot be used against the application.