Amend rules for determining priority of patent claims to prevent self-collision ("poisonous priority")

At a glance

Policy ID: 18

Status: Policy development

Priority: Medium


Issue summary

In rare circumstances, it's possible for the disclosure of a priority document to be novelty destroying for a subsequent application by the same applicant, despite claiming priority from the first document. This can happen when multiple alternatives are presented in a single claim, only some of which are entitled to the earliest priority.

Section 43 of the Patents Act is intended to prevent this occurrence by allowing claims to multiple forms of the invention to have multiple priority dates, but has been interpreted narrowly by the courts, arguably defeating the policy intent of the section.

Clarification of section 43 may address this situation and prevent an applicant's own priority document being prejudicial to the novelty of their subsequent filing.


  • Policy Development 4 September 2017
  • Reviewed February 2021


Work is being undertaken to identify the scope of the problem and whether legislative change is necessary.

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