Priority filings and the Canadian Grace Period
A priority patent filing is normally understood to shelter an applicant from any public disclosures that may be made by themselves or others in the priority year following thereafter. This is true in respect of inventions that were not made available to the public before the priority filing date. But it is not true in respect of inventions which were disclosed publicly before that date, even though the right to obtain a US patent is still available based on the US one-year grace period.
If a third party has disclosed an invention publicly before the date of a priority patent filing, then it is too late to file an application in Canada in respect of the subject matter that has been disclosed.
Once a priority date has been obtained, it will shelter the Canadian application against all public disclosures occurring thereafter during the priority year. This is true irrespective of the source of such disclosures. Under these circumstances, it is not necessary to file the Canadian application promptly unless the invention has been disclosed publicly by the inventor previous to the priority filing date.
Canada has a one-year grace period to shelter an application against disclosures made by the applicant. This one-year grace period extends back from the actual Canadian filing date. It does not extend back from the priority date. Accordingly, if the original inventor or any person deriving knowledge of the invention from the original inventor has made a disclosure of the invention to the public (this could mean any member of the public not burdened with a duty of confidentiality), then an actual application must be filed in Canada within one year from the earliest date of such a disclosure.
If the facts permit, it may be advantageous to delay the Canadian filing until the end of the priority year because this will extend the length of the Canadian patent by one year. Additionally, new matter may be added in any filing made towards the end of the priority year. The new matter will not be credited with the original priority date, but the balance of the application will enjoy the benefit of the original priority date.
This information is relevant for US attorneys contemplating filing an application in Canada, particularly in cases where the US client is relying on the grace period available in both countries. It is also relevant as there is a prospect that the Canadian grace period system will be adopted by the United States as part of the US patent law reform process.