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. Conditions for filing

Date Published

Key Legislation

Patents Act:

  • s61(2) Grant of standard patent
  • s79B Divisional applications prior to grant of patent
  • s80 Chapter does not apply to innovation patents 
  • s81(1)(a)-(2) Chapter does not apply to innovation patents
  • s83 Term of patent of addition
  • s85 Revocation of patent for main invention
  • s86 Renewal fees not payable

Patents Regulations:


Chapter 7 of the Act provides for the grant of a ‘patent of addition’. A patent of addition allows an applicant or patentee to claim an improvement or modification to their invention (“the main invention”) defined in a parent application or patent.

Section 80 states that patents of addition do not apply to innovation patents. Thus, neither the parent, nor the patent of addition, can be an innovation patent.

In general, the conditions for the filing of standard patent applications also apply to applications for patents of addition. The following section outlines some of the specific requirements for Patents of Addition.

What is the “main invention”

The "main invention" of s81(1)(a) is the invention claimed in the complete specification of the parent application or patent. This is distinct from an invention that is merely disclosed in it.

Where the parent application is subsequently divided under s79B, examiners are to ensure that the patent request for the patent of addition is amended (where necessary) to identify the parent application in which the main invention is ultimately to be found.

Additional to an Additional

In the case of applications for a patent of addition to a patent of addition, the “main invention" of the second application for a patent of addition is the invention which is the subject of the first patent of addition (or therefore the application) and not the initial parent patent. Similarly, where there is a longer chain of additionals to additionals, the "main invention" for the purposes of s81(2) is that of the immediately preceding application or patent. Thus, additionals to additionals can take place only in chronological order (see also Plural Additional Applications).

Patent Request

The patent request must indicate that it is for a patent of addition and state the parent application or patent number. ​​​​​​​

Parent Must be in Force

Section 81 does not explicitly preclude the filing of an application for a patent of addition where the parent is not in force. However, the requirement under s83 that the patent of addition remains in force for as long as the parent patent remains in force would render such an application meaningless.

Therefore, examiners should check at each report stage whether the parent is in force. If the parent is not in force, then an objection should be taken that the application cannot proceed as a patent of addition. Opinion on all other matters should be reserved pending resolution of whether the application is to proceed as an application for a standard patent (see Improvement or Modification).

Note that in rare circumstances, a patent of addition may become independent of the parent patent. These include where the parent patent is revoked (s85) or the term of the patent of addition is extended (s83; see also 7.12.5 Patents of Addition). In either circumstance, examiners should refer the matter to Oppositions.

Timing Provisions

The "date of the patent for the main invention" for the purposes of reg 7.1(2) is the date when the first complete specification disclosing the main invention was filed. A patent of addition cannot be granted when the first disclosure of the main invention occurs after the filing of the application for the patent of addition. Careful consideration of this matter is required when the main invention is described in either an amended patent, or in a divisional application where further information is added.

Grant Requirements

A patent of addition must not be granted before the patent for the main invention is granted (s81(3)).  In practice, examiners must not accept an application for a patent of addition until the parent application has been accepted. However, in certain circumstances, the grant of the parent patent may be accelerated and the grant period of the additional patent may be extended (see s61(2) and reg 6.2(1)(b)). Cases involving timing complications of this type are to be referred to a supervising examiner.

Plural Additional Applications

There may be several applications for patents of addition filed in respect of one main invention and they may be related to one or several of the claims of the parent specification. There is no objection if any of the applications for a patent of addition is filed at the same time as the application in respect of the main invention.

Additional to an Additional

A patent of addition may be applied for, and granted, in respect of another patent of addition (see McFeely's Application [1912] 29 RPC 386). There is also no objection if there is a longer series of additional applications. However, it is essential that the patent request discloses all relevant facts, such that the term of any patent issued can be readily determined.

Both an Additional and Divisional

An application can be an additional to one application (or patent) and a divisional of a different application (or patent). The term of an additional will be the same as its parent (that is, the application or patent for the main invention) regardless of whether it also claims divisional status.

In order for an application for a divisional and an additional of the same parent to be accepted, all of its claims must satisfy the criteria of both a divisional and an additional application.

It is difficult to envisage this occurring under normal circumstances given that an "improvement or modification of the main invention" cannot be matter disclosed in the parent application (see Improvement or Modification). However, in the case of application 17561/00 (759625), an independent claim comprised two notional claims, one of which met the criteria for being a divisional of 36806/97 (736856), and the other which met the criteria for being an additional of the same parent.  The applicant sought both divisional and additional status for the application. This was considered permissible, and the application was allowed to proceed to grant.

The "Fees" section below provides details on the continuation/renewal fees applicable in these circumstances. Status of Parent provides guidance on the situation where an application is a divisional application of a patent of addition.


Continuation fees are payable in respect of an application for a patent of addition. The date for determining the payment of continuation fees is the filing date of the patent of addition application (reg 13.3(1)). However, no renewal fee is payable on a patent of addition (s86) and the patent of addition normally ceases when the parent patent ceases (s83(1)).

Where an application is both a divisional and an additional, the continuation fee payable is determined on the basis of its status as a divisional application. However, upon grant, the renewal fee is determined on the basis of its status as a patent of addition, that is, no renewal fee is payable.

Amended Reasons

Amended Reason Date Amended

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