We applied for US and Canadian Utility Patents. Our US patent issued. After the US patent issued, during prosecution, the Canadian patent examiner sent back an office action and cited prior art that we did not cite in the US application. What do we do now.

1 Answer 1


Information that comes to your attention before the grant of your U.S. patent must be brought to the attention of the USPTO even if it is after the notice of allowance and payment of the issue fee. After grant there is no obligation to do anything with this new reference. However, if you feel it weakens the patent, you might request an ex parte reexamination. This will allow the new reference to be considered, and arguments and amendments to be made. You may end up with a narrowed but stronger patent.

  • So if we answer the Canadian Office Action that cites the prior art that was not cited in the US application does that expose the US patent to any problems? And if the Canadian patent issues does that reflect on the US patent. Will that weaken the US patent?
    – Paula
    Commented Oct 22, 2013 at 18:41
  • The existence of the prior art reference is what weakens your patent. The Canadian Office Action will be a matter of public record at some point if it isn't already. This is not legal advice and if you are patenting in multiple countries I think you should get legal advice. But I would think that a response to Canada as to why the reference does not knock out your claims that they end up agreeing agree with would tend to strengthen your U.S. patent in the eyes of potential infringers or people considering initiating a re-examination or review.
    – George White
    Commented Oct 22, 2013 at 20:25

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