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A patent's filing and priority date. What is the difference? | EP&C


The front page of a patent contains various dates: a priority date, a filing date and - once the patent has been granted - a grant date. This can be confusing and can even lead to major financial problems if, for example, you want to find out how much longer your competitor's patent is going to be standing in your way (and you start out from the wrong date). That is why I am providing an explanation of the various dates in my BL&G this time as well as what to watch out for.

Priority date of a patent

The priority date of a patent is the date on which you first file a patent application in respect of your invention. The application could be for a Dutch or a Belgian patent, or for a patent in any other country. You can make your invention public from this moment on as your idea has been registered as your invention.

This is referred to as the priority date of the patent because it enables you to invoke 'priority' or a 'priority right'. Isabelle gives an example of the priority date in her BL&G.

Filing date of a patent

You have had your invention secured in an initial patent application. However, if you want to protect your innovation in other countries too, you will need to file a further application within a year. You can do so in another country, such as Germany, but can also file a European patent application or a PCT application.

The filing date of a patent refers to the date on which you filed your further application in a particular country or territory. This is the date from which the maximum validity of 20 years starts.

Grant date of a patent

The grant date of a patent is the date on which the official body (Netherlands Patent Office / European Patent Office) grants the patent.

For a Dutch patent this is always 18 months after the priority date, because we work with a registration system. A European patent can be granted within two years, but it may also take longer: in exceptional cases it can take ten years or more.
From the grant date you can officially invoke your rights in the event of an infringement. However, you can still draw the attention of infringers to the fact that your patent is pending prior to your patent being granted and claim damages for an infringement during this patent pending phase once the patent has been granted. This will be examined in more detail in one of our future BL&Gs.

What do I need to remember?

  1. Your innovation is secured by a patent from the priority date. You can then make your invention public.
  2. If you want to know when a patent expires, you will need to take the filing date as a basis and add 20 years. That will generally be sufficient (although there are exceptions). 
  3. You can take legal action against infringers from the moment your patent has been granted. Prior to this date there are other avenues that can be pursued.
  4. If you want to know for sure that a patent is still valid, you should check this out with a patent attorney. A patent may appear to be valid, but if not all of the conditions have been met, the right may be invalid or have expired.