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Date Published

Key Legislation:

Patents Act:

  • s102 What amendments are not allowable​​​​​​​


Supporting evidence will usually be required where a requested amendment is for the purpose of correcting a clerical error or obvious mistake and would otherwise not be allowable under s102, such as if it introduces new matter or falls outside the scope of accepted claims.

If the amendment does not contravene s102, no evidence is required.

​​​​​​​Examination practice

Generally, in order to establish the existence of a clerical error, evidence in the form of a declaration that fully explains the facts surrounding the clerical error and the amendment sought will be required.

For correction of an obvious mistake, evidence will be needed to establish that the instructed reader of the specification would clearly understand that a mistake had occurred and would know the correction intended.

Legal principles

Clerical error

The nature of a ‘clerical error’ was considered fully in R. v The Commissioner of Patents; Ex parte Martin 89 CLR 381. The majority judgement in that case noted:

"The characteristic of a clerical error is ... that it arises in the mechanical process of writing or transcribing."

Similarly, in Maere’s Application [1962] RPC 182 at page 185, the hearing officer said:

"The words ‘clerical error’ ... mean a mistake made in the course of some mechanical process such as writing or copying as distinct from an error arising, e.g. from lack of knowledge, or wrong information, in the intellectual process of drafting language to express intention."

The incomplete revision of a template document in line with instructions has been found to be a clerical error (see BHP Billiton v Cominco Engineering (2009) APO 10).

However, an error in reasoning cannot amount to a clerical error (see Austal Ships v Stena Rederi (2009) FCAFC 179 at paragraph 25).

Where the applicant or patentee seeks the benefit of s102(3), (on the basis of a clerical error having been made) the onus is on them to make out an appropriate case for the proposed amendment, including proof of the error (The Distillers Co. Ld’s Application [1953] 70 RPC 221).

Obvious mistake

An obvious mistake is one:

"... that the instructed public can, from an examination of the specification, appreciate the existence of the mistake and the proper answer by way of correction."

(General Tire and Rubber Co. (Frost’s) Patent [1972] RPC 259 at page 279).

Substitution of a specification for one allegedly filed by mistake was not allowed in the case of Farbenfabriken Bayer A.G.’s Application [1970] AOJP 4333.

The term ‘correction’ means the putting right of some mistake that has been made in preparation of the specification (The National School of Salesmanship Ltd v The Plomien Fuel Economiser Ltd (1942) 59 RPC 95 at page 107). ‘Correction’ should not be regarded as covering errors of judgement in the preparation of the specification as to what should be included in the claims, provided that the document, as drafted, accurately represented the intention of the draftsman at the time of drafting (Distiller Co. Ld.’s Application [1953] 70 RPC 221).

As stated in A.E. Staley Manufacturing Co.’s Application [1966] AOJP 1780 at page 1781:

"An error of judgment on the part of the draftsman ... is not an obvious mistake."

In Tee-Pak Inc.’s Application [1958] RPC 396 at page 398, it was stated that:

"... to constitute a mistake there must be an erroneous transcription of the draftsman’s intention to express in words the description of the invention for which patent protection is sought, the manner of its performance or monopoly claim or claims made in relation to it. The word ‘obvious’ imposes as a further qualification, the requirement that such error must be plainly evident and must be construed in an objective sense to mean so evident from an examination of the documents in the case."

A correction does not fail to be obvious merely because as a matter of drafting, there is more than one way of expressing it without affecting its meaning (Holtite Limited v Jost (Great Britain) Limited and Others (1979) RPC 81 at page 91).

Subsequent research does not make something ‘an obvious mistake’ which was believed correct at the time of drafting (The Griffith Laboratories Application [1967] AOJP 1603).

In Egyt Gyogyszervegyeszeti Gyar’s Patent [1981] RPC 99, an application was made for a chemical compound defined by structure, molecular formula and melting points of derivatives. Subsequent research found the structure to be incorrect and it was proposed to insert the correct structure by amendment. Whilst it was argued that it was obvious that the original formula was a mistake, the new one was not allowed. However, a claim to the compound defined by its molecular formula and melting points was allowed.

The Court found that it was obvious in reading the specification as a whole that the patentees had intended to claim the product having particular characteristics of molecular formula and melting point:

"... The point is what he wanted to do was to claim the result of carrying out that process. It now turns out to be the fact that the result of carrying out the process is not an imide but a diazepine. In those circumstances, it is right, when referring back to the specification, to say that not only is there an obvious mistake but also it is obvious what the answer ought to be and, therefore, he can make an amendment in accordance with section 31 even if the resultant amended claim in the specification could not be said fairly to fall within the scope of the original specification at all ..."

See also: 

Pittsburgh Plate Glass Co.’s Patent [1971] RPC 55;

Zambon S.p.A.’s Patent [1971] RPC 95;

Dempster Brothers Inc.’s Application [1974] AOJP 4276; and

Berg and Stromberg’s Application [1985] APOR 15.

Amended Reasons

Amended Reason Date Amended

Published for testing

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