IP-Academy

Restoring Lost Patent Priority Rights: What You Need to Know about “Due Care” and “Unintentional” Criteria
Losing your patent priority rights can feel like a serious setback but in many cases, you may be able to restore them. Depending on the country and circumstances, two main legal grounds can support reinstatement:
You acted with due care, or the delay was unintentional.
Let’s take a closer look at how each option works.
What Are Patent Priority Rights?
When you file a patent application, you typically have 12 months to file related applications elsewhere while keeping your original filing date. This is called your “priority right”.
If you miss this deadline, your right to claim priority may lapse — but many countries that follow international agreements like the Paris Convention or the Patent Cooperation Treaty (PCT) offer a way to restore it. For example, under the PCT, you have up to 2 months after the missed deadline to request restoration as long as you meet either the due care or unintentionality standard.
Option 1: Restoration Based on Due Care
This is the more demanding option. You must show that you did everything a reasonable and careful applicant would have done and still missed the deadline despite your efforts. Examples of valid reasons may include:
Illness or absence of you or your agent
System failures or technical problems
Miscommunication with your agent
Mistakes by staff or clerical errors
Postal service delays or force majeure events (e.g. natural disasters)
You’ll need to provide a detailed explanation of what happened, along with any supporting evidence. The patent office will review your actions up until the deadline to determine whether you truly exercised due care.
Option 2: Restoration Based on Unintentional Delay
This standard is less strict. To qualify, you must show that the missed deadline was not intentional — that is, you meant to file on time, but something went wrong. Common situations that may qualify:
You misunderstood the filing requirements or laws
You were unaware of the deadline
You relied on incorrect information or advice
Here, the focus is on your intent, rather than whether your actions met a high diligence standard.
Submitting a Statement of Reasons
Whether applying under due care or unintentionality, you’ll need to file a Statement of Reasons explaining:
Why you missed the priority deadline
Which criterion you’re relying on (due care or unintentional)
Any supporting documents (e.g. emails, system logs, medical records)
The receiving patent office will review your statement and may request more information if needed. A strong, well-documented explanation improves your chances of success.
Summary
While losing a priority right can feel like a major obstacle, you may still have options to recover it, especially if the delay was unintentional or you acted with reasonable care. However, restoration is time-sensitive, so act quickly. If you’re unsure which route to take or how to prepare your application, professional guidance can be of great assistance.
Need help? Contact us through our website: www.ip-coster.com