Last updated: 
22 November 2018

A patent of addition can be applied for if you already have a standard patent application (the parent) and you want another patent for an improvement or a modification to the original invention.

As the name suggests, a patent of addition must describe an improvement or modification that has not already been described in the parent application.

Patents of addition are for minor improvements of modifications. If the improvement is significant then you may need to apply for a new standard patent.

You can apply for a patent of addition using online services.

The specification and claims for a patent of addition should be prepared in the same way as a normal specification for a standard patent. There are only a few slight differences:

  • You may find it useful to identify the main invention described in the parent, and then describe the improvement or modification that you have made.
  • You may want to make reference to one or more claims from the parent specification when writing your new claims. For example, '1. A bed sheet tensioner as claimed in any one of claims 1 to 6 of patent number 654321, wherein...'

Requirements for a patent of addition

There are some key requirements that need to be met when applying for a patent of addition:

  • A patent of addition cannot be an innovation patent and cannot have an innovation patent as a parent. (The innovation patent is being phased out, learn more).
  • A patent of addition cannot claim matter that was disclosed in the parent specification.
  • A patent of addition cannot exist on its own, so the following conditions apply:
    • We will not examine an application for a patent of addition unless you have asked us to examine the parent application. We will not accept an application for a patent of addition unless the parent application has been accepted.
    • A patent of addition cannot be granted until the parent patent has been granted.
    • A patent of addition will not be accepted or granted if the parent has ceased. However, if the parent does cease you have the option to convert your application for a patent of addition into a normal standard patent application. Patents cease if you fail to renew them or if they reach the end of their 20 year term.
  • The application for a patent of addition must be filed on or after the date on which the parent was filed.


Before a patent of addition is granted, it needs to be maintained like a normal standard patent. This includes fees for:

  • filing your application
  • examination
  • renewal (payable yearly from four years after the application was filed, until it is granted).

Once a patent of addition is granted, renewal fees are only required to be paid for the parent application. No additional fees are required for the patent of addition itself. Once the parent patent ceases, so does the patent of addition.

Get professional advice

Patent matters can involve complex legal issues and it may be in your best interests to consult a patent attorney, solicitor or business adviser experienced in intellectual property.