What does priority date mean?

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 non-provisional 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 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 non-provisional application, then your priority date is the non-provisional filing date.
  • If your earliest-filed application was an international or foreign-filed application, then the filing date of the non-US application is your priority date.

Why do 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 before your priority date 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. Non-provisional 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 priority date is preferable. If a priority date can be maintained, then by implication it can also be lost particularly when a patent family is involved.

One of the most common ways to forfeit a priority date is the failure to convert a provisional to a non-provisional 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.

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Vic Lin

Vic Lin

Startup Patent Attorney | IP Chair at Innovation Capital Law Group
We love working with startups and small businesses. I help entrepreneurs protect their intellectual property so they can reach their business goals.