What is a patent priority date?

Priority date refers to the earliest filing date in a family of patent applications. Where only a single patent application is involved, the priority date would obviously be the filing date of the sole application. If an applicant has filed a number of related patent applications, the priority date would be the filing date of the earliest patent filing that first disclosed the invention. Known as the priority application, the earliest patent filing may comprise a provisional patent application, a nonprovisional patent application or a foreign application.

The term may also refer to the earliest filing date of a particular feature of an invention. Therefore, it is possible to have multiple priority dates if new features were subsequently added in related applications.

Different types of patent priority dates

Depending upon your particular situation, your priority date will be the following:

  • If your earliest-filed patent application for a particular invention was a provisional application, then the filing date of the provisional is your priority date.
  • If your first filing was a nonprovisional application, then it would be the nonprovisional filing date.
  • If your earliest-filed application was an international or foreign-filed application, then it would be the filing date of the non-US application.

Why do patent priority dates matter?

The priority date is how we determine whether another patent filing or publicly available document qualifies as prior art against your patent application. Generally, patent applications filed and publicly available documents published before your priority date will be considered prior art.

For example, suppose you filed the following patent applications:

  1. Provisional filed on Jan. 20, 2016 disclosing features A and B of an invention;
  2. Nonprovisional filed on Jan. 20, 2017 claiming priority to the 1/20/16 provisional and adding new feature C (i.e., disclosing A, B & C); and
  3. CIP filed on Aug. 20, 2017 adding new feature D (i.e., disclosing A, B, C & D).

In the above hypothetical situation, the following priority dates would result for each feature:

  • Features A & B: 1/20/16 (filing date of provisional);
  • Feature C: 1/20/17 (filing date of non-provisional); and
  • Feature D: 8/20/17 (filing date of CIP).

Basically, each feature has a priority date of when it was first filed. Since new features are provided with a later priority date based on when they were first introduced in a patent filing, it’s best to file the related applications as soon as possible whenever a new feature/modification/version is deemed patent-worthy.

How to maintain a priority date

Since the USPTO operates under a first-to-file rule, maintaining the earliest possible filing date is preferable. The benefit of an earlier filing date may may be lost due to inaction or delay.

One of the most common ways to forfeit the benefit of an earlier filing date is the failure to convert a provisional application to a nonprovisional application within one year from the provisional filing date. Re-filing the provisional results in a later priority date, which consequently opens up potentially more prior art that can be used against you.

For international and foreign applications, such foreign filings generally must take place within one year of the US priority date unless a PCT application is timely filed to extend the deadline for national applications to be filed in each individual foreign country.


The following two tabs change content below.

Vic Lin

Startup Patent Attorney | IP Lead Partner at Innovation Capital Law Group
We align ourselves with Davids fighting Goliaths. Our registered patent attorneys work as a team to equip startups and founders with solid IP rights that facilitate funding, growth and sales. Email or call us so we can get to work on your IP: (949) 223-9623 | vlin@icaplaw.com