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8.11.1 Priority Date of Claims

Date Published

Key Legislation

Patents Act:

  • s35 Applications by eligible persons following revocation by Commissioner  
  • s36 Other applications by eligible persons  
  • s40 Specifications  
  • s43 Priority dates  
  • s79B Divisional applications prior to grant of patent  
  • s79C Divisional applications for innovation patents may be made after grant of an innovation patent  
  • s114 Priority date of claims of certain amended specifications  

Patents Regulations:

  • reg 3.13 Priority date for application by person declared under section 36 of the Act
  • reg 3.14 Priority dates: certain amended claims
  • reg 8.1 (Superseded)
  • Chapter 3 From application to acceptance

Patent Cooperation Treaty (PCT)

Related Chapters:

  • 2.11.7 Claims are Fairly Based
  • Priority Date Issues Relating to Amended Claims
  • Priority Sources

On this page

  • General 
  • Determination of Priority Dates
  • Level of Disclosure Required
    • Tests for Determining Disclosure
    • Selections
  • Claims With More Than One Priority Date
  • Specifications Containing Claims With Different Priority Dates
  • Case Law


Under s43(1), each claim of a specification must have a priority date.  The priority date of a claim is primarily of relevance when assessing the claim against the criteria of novelty and inventive/innovative step.

The actual priority date of a claim is determined by the provisions of the Act and Regulations. However, during search and/or examination it should usually not be necessary in the first instance to determine the actual priority date of a claim.  When conducting a search, examiners should keep in mind both the earliest priority date and the latest possible priority date (i.e. the date of filing). If, as a result of the search, a document is found which would constitute a citation against a claim only if the claim is not entitled to the earlier priority date, examiners should proceed to determine the priority date of the claim in question.

However, where the determination of priority dates is difficult or time consuming, it is not unreasonable to take the date of filing as the prima facie priority date, with the onus of rebuttal being placed upon the applicant or attorney.

Note: In certain situations, an application under examination may claim priority from a published document, such as a PCT application.  That PCT application may in turn have its own priority document, which may have been filed more than 12 months before the filing date of the application being examined.  Where these circumstances arise, examiners should check the priority date of the claims.

Note: In relation to an international application, reg 8.1(1) and Article 2(xi) of the PCT define a "priority date" for the application for the purposes of computing time limits. This has no bearing on the priority date of claims as discussed below.

Determination of Priority Dates

Under s43(2), the priority date of a claim is:

a. the date of filing of the specification; or

b. where the Regulations provide for the determination of a different date as the priority date – the date determined by the Regulations.

A single complete application may derive priority by operation of more than one provision of the Act and Regulations, for example as a Convention application, a divisional application or by association with a provisional application. Priority dates are determined by Chapter 3, Part 1 of the Regulations.

In general, if a claim is fairly based on matter disclosed in a priority document or a "parent application" (for a complete specification filed in respect of a divisional application), then the priority date of the claim is the date of filing the priority document or "parent application".

Regulation 3.12 provides for most priority dates including:

  • claims of a complete specification associated with one or more provisional specifications;
  • claims of the specification of a Convention application, where there was more than one specification filed in connection with a basic application;
  • claims of the specification of a PCT application which may have one or more earlier Australian applications, or one or more basic applications;
  • claims of a complete specification filed pursuant to s79B (divisionals);
  • claims of a complete specification filed pursuant to s79C (divisional applications for innovation patents); and
  • claims of a divisional application where deposit requirements in relation to micro-organisms have not been satisfied.

Note: Special priority considerations which apply to applications made under the PCT route are discussed in Priority Sources.

In certain circumstances, the Act and Regulations may also determine further priority dates different from the date of filing of the complete specification.

The provisions which cover these priority dates are:

  • s35, s36 and s43(2)(b) and reg 3.13 – where claims of a complete specification are filed pursuant to the operation of s35 and s36; and
  • s114 and reg 3.14 – where claims of a complete specification claim matter in substance disclosed only as a result of the amendment (see also Priority Date Issues Relating to Amended Claims).

Level of Disclosure Required

The priority date of a claim is the date of filing of a specification which first discloses matter upon which the claim is fairly based and from which the claim is entitled to claim priority. The fair basis requirements in order for a claim to obtain priority are substantially the same as for the claims to be fairly based in accordance with s40(3) (see 2.11.7 Claims are Fairly Based).

Subsection 40(3) requires that the claims of a specification shall be "fairly based on matter described" in the specification. In The International Paint Company Limited's Application (1982) RPC 247, it was held that the words "described" and "disclosed" in the UK Patents Act 1949 meant precisely the same thing in relation to a document which was being considered as a whole. In this context, examiners can assume that the words have the same meaning under the Australian Patents Act 1990.

Tests for Determining Disclosure

The fundamental requirement for a claim to be fairly based on a particular disclosure is that the disclosure must contain a "real and reasonably clear disclosure of the subject matter of the claim" (CCOM Pty Ltd v Jiejing Pty Ltd 28 IPR 481; (1994) AIPC 91-079 and Sartas No. 1 Pty Ltd v Koukourou & Partners Pty Ltd and Nicola Leonardis 30 IPR 479; (1995) AIPC 91-121).

The following tests provide guidance in determining whether a real and reasonably clear disclosure has occurred:

  • If a claim meets the "Mond Nickel Rules" set down in Mond Nickel Company Ltd.'s Application (1956) RPC 189 at page 194 it will be fairly based on the priority document. In Imperial Chemical Industries Ltd.'s Appln. (1960) RPC 223, the test was further expanded:

"the word 'broadly' was used in respect of the description and carried the meaning of 'in a general sense', such as would be exemplified by a statement in the provisional specification that reaction products were dissolved in hot water, where the complete specification introduced a specific temperature range ....”

  • Unless a prior specification discloses all the essential features of a claim, it will not constitute a fair basis for the claim (Interact Machine Tools (NSW) Pty Ltd v Yamazaki Mazak Corporation 27 IPR 83; (1993) AIPC 91-026 and Anaesthetic Supplies Pty Ltd v Rescare Ltd 28 IPR 383; (1994) AIPC 91-076).

In the latter decision, the court added a further requirement, i.e. where the priority document is a provisional specification, every essential feature disclosed in the priority document must be included in any claim for which priority is sought from the provisional specification. However, later court decisions have cast doubt on the correctness of this approach and examiners must not apply this criterion for examination purposes.

A claim may properly derive priority from a prior specification where the specific matter added to the disclosure of that specification is common general knowledge (Scherico Ltd.'s Appln. (1968) RPC 407).  For example, if the prior specification does not disclose the material of which a particular part is made, but it is common general knowledge (at the relevant date) that such a part may be made of a certain material, then the specification may be regarded as disclosing the part made of that material. If examiners are unaware that certain matter is common general knowledge, it may be assumed not to be until evidence to the contrary is provided. The extent and nature of the evidence required is the same as that required of examiners citing common general knowledge during examination.


Where an invention resides in a selection, the claims of a complete specification will not be fairly based on matter disclosed in a priority document, if the claims are directed toward a selection which is not disclosed in the priority document. This should be particularly kept in mind where, as a result of an amendment in response to a novelty and/or inventive step objection, the invention of the complete specification becomes one of selection, or becomes a materially different selection from that originally disclosed in the priority document (see Cooper's Animal Health v Western Stock Distributors (1987) 11 IPR 20).  However, where a feature in a claim is merely restricted to a subset of alternatives taught in the specification and the alternatives are taught in the priority document, the priority document will contain a sufficient disclosure of the claimed subset.

Claims With More Than One Priority Date

A claim may possess more than one priority date.  Under s43(3), where a claim of a complete specification defines more than one form of an invention, then the claim must be treated as constituting a separate claim for each form of the invention for priority date purposes. Consequently, a claim may possess more than one priority date. Examples where this may occur include:

  • a claim directed to alternative forms first disclosed in separate documents;
  • a claim appended to a number of claims having different priority dates; or
  • an omnibus claim referring to drawings or examples disclosed on different dates.

In this case, the words "form of the invention" mean matter which clearly falls within the concept of the invention, as the claiming of different inventions in one claim is precluded under s40(4). Each separate "form of the invention" can, by virtue of s43(1), have only one priority date.  

However, as discussed in AstraZeneca AB v Apotex Pty Ltd [2014] FCAFC 99 at [251]; 107 IPR 177, not every potential variant of the defined invention can be treated as a different form of the invention which is to be given its own priority date.

Whether an invention has different forms was also considered in Nichia Corporation v Arrow Electronics Australia Pty Ltd [2015] FCA 699 at [58] – [87].  In this case, the claims were cast in terms that envisaged and provided for different forms of the invention, in contrast to the claims considered in AstraZeneca supra.

Specifications Containing Claims With Different Priority Dates

Under s43(4), the claims of a specification may have different priority dates. These different dates may result from, for example, a complete specification deriving priority from more than one priority document, or in the case of a divisional application, from more than one “parent application”.

Case Law

Decisions in which the determination of priority dates was an issue include:

  • British Drug Houses Ltd.'s Appln. (1964) RPC 237

In the absence of any suggestion in the complete specification that there was invention in restricting the starting materials claimed, compared with those disclosed in the provisional specification, the claims were entitled to the earliest priority date, i.e. the filing date of the provisional.

  • Farbenfabriken Bayer A.G.'s Appln. (1973) RPC 698

A claim to a process was fairly based on the disclosure of the provisional specification, since if the apparatus there described was made and the process performed, it would in fact operate as stated in the claim.

  • Hoffmann-La Roche & Co. AG v Commissioner of Patents (1971) 123 CLR 529

Claims to compounds in a Convention application were fairly based on the first basic application, even though the process disclosed in that application would lead to the production of many other compounds and the compounds were disclosed in later basic applications.

  • International Playtex Inc.'s Appln. (1979) AOJP 1188

The claims in the specification omitted a feature described in a priority document as essential to the invention and thus lacked fair basis.

  • Dunn v Ward 1 IPR 595

Two features of the claims were not disclosed in the provisional specification. The claims were only entitled to the later priority date, i.e. the filing date of the complete specification.  

  • Cooper's Animal Health v Western Stock Distributors 11 IPR 20

An essential constituent of a claimed formulation was a particular solvent in a specified quantity. This solvent was mentioned in the provisional specification only as one of a number of possible alternatives and other solvents were discussed in a more favourable light. The special advantages arising from the use of the particular solvent were not apparent from a reading of the provisional specification.

The Court found that identification of that constituent as a key element of the claimed invention could properly be regarded as involving an inventive step, however the claim was not fairly based on the provisional specification. A relevant factor in the decision was that the claimed invention was the formulation, whereas the invention disclosed in the provisional specification was a method of treating sheep.

It should be noted that the decision that the claim was not fairly based did not result simply from the fact that a feature which was optional in the provisional specification was included in the claim. Rather, it was based on the conclusion that the whole nature of the invention had changed between the provisional and complete specifications.

Amended Reasons

Amended Reason Date Amended
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