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Amending a patent after it is granted can be an important first step to enforcing the rights to that patented invention. It is therefore important to understand when and how post-grant amendments may be made given that the availability of such a mechanism differs between jurisdictions, as do the applicable rules and regulations.

Can a granted patent be amended? 

The rules regarding patent amendments in Australia change at the date of acceptance of an application and those same rules apply post-grant.  For the most part, amendments after acceptance are allowed in Australia.  However, such an amendment is not allowed if it results in a claim that does ‘not in substance fall within the scope of the claims of the specification before amendment’.  The only exceptions to this scope-widening condition are where the amendment is for the purposes of correcting a clerical error or an obvious mistake, or complying with micro-organism deposit requirements.

Clerical errors and obvious mistakes

A clerical error has been established as a mistake made during a mechanical process such as writing, copying or transcribing. For example, a clerical error arises when a person, under instructions from someone else, inadvertently omits material or writes something other than what was intended.

To be considered an obvious mistake two important requirements must be met: from looking at the specification, both the existence of the mistake and its correction must be apparent to the reader. A good example of what does not meet this second requirement is where a page of a specification is missing. If say, the pages number 1-12 and 14-20, it is clear that page 13 is missing, but the correction cannot be determined since it is not known from looking at the specification what the content of page 13 should be.

If relying on the clerical error or obvious mistake provisions, the onus is on the applicant to prove the error or mistake, usually by evidence in the form of a declaration.

Other allowable amendments 

If neither of the above exceptions are applicable then the amendment cannot extend the scope of the claims. To determine whether an amended claim falls outside its original claim scope, a comparison must be made between the amended claims and the claims immediately before the amendment. Therefore, if the accepted claims were previously amended, the original claims are not assessed.

The ‘scope of the claims’ means the scope of the entire claim set, not merely the scope of one or more claims. All claims must be considered, and the subject matter defined by the claims can be added together. However, cherry-picking of particular features or details from different claims that results in a previously undefined invention is not allowed. By way of example, an amendment to claim 1 of a patent that introduced subject matter previously found in claim 8 would be allowable. While such an amendment introduces new subject matter into claim 1, that subject matter fell within the scope of the claims when viewed as a whole, before the amendment.

To further assess whether a post-grant amendment is allowable and does not broaden the scope of the claims, a relevant test is whether the amendment makes anything an infringement which would not have been an infringement before the amendment. If the answer is yes, the amendment is not allowable.


If the amendment is allowable according to law, the Patent Office must progress it. However, before the amendments can be formally entered into the official record, a final hurdle must be crossed. On the principle that once granted, a patent sets out where the boundaries of infringement lie for competitors and changing those boundaries may prejudice a competitor, all post-grant amendments are advertised for opposition purposes. If no opposition is forthcoming, the patent specification of record is formally changed to include the amendments.

Amendments during court proceedings 

The Patent Office cannot allow amendments if proceedings in relation to a patent are pending. Instead, the Court will consider the proposed amendment. Importantly, in addition to considering whether the amendments are allowable according to the law, the Court has a broad discretion to consider other factors.  Critically, the Court can chose to exercise this discretion and refuse otherwise allowable amendments (such as those discussed above). The full Federal Court has done this in the past[1], citing both the patentee’s delay and failure to disclose its reasons for seeking amendment, as the basis for refusing amendments that otherwise met the requirements of a valid post-grant amendment.

Why would a granted patent need amending?

Getting ready to enforce a patent is just one reason why post-grant amendment might be contemplated. There are a number of other reasons a patentee might need or want to make amendments to their granted patent, such as the uncovering of a new piece of prior art or more simply, just to clarify a detail to avoid misinterpretation of the invention. Post-grant amendment may also be forced on a patentee by a third party through a reexamination proceeding.

The High Court once stated:

‘an amendment may be allowed where it does no more than explain what is already in the claim when it is properly construed. It may be said that such an amendment is unnecessary because it adds nothing to the claim so construed. However, when it is borne in mind that the claim is intended to speak to the world, an amendment by way of explanation so that any misapprehension can be avoided may clearly be desirable.’[2]

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