Welcome to the new version of the Patents Manual. Please note there are changes to the numbering and sequence of the chapters and pages in the manual. You are encouraged to take the time to explore and familiarise yourself with this new structure. Definition of obvious mistake

Date Published


An obvious mistake is one where a reader of the specification can clearly identify that a mistake has occurred, that a reader would have no difficulty in knowing what was intended, and what the correction would be.

Examination practice

It can be difficult to know what was intended. For example, while it may be clearly apparent that a sheet of the specification is missing, it may not be obvious what sheet should have been there in the first place.

The correction of ‘obvious mistakes’ should not be used to cover errors of judgement by the person who drafted the specification. Such errors would not be obvious to the public.

A correction can be expressed in multiple ways, as long as the meaning of the correction is the same as the meaning originally intended.

Subsequent research does not make something an ‘obvious mistake’ if it was believed to be correct at the time of drafting. For example, an application was filed for a chemical compound defined by its structure. Subsequent research found the structure to be incorrect, but amendment of the new structure was not allowed as it was not an obvious mistake at the time of drafting.

Amended Reasons

Amended Reason Date Amended

Published for testing

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