Myths of IP – Part 1 – The Copyright “10% rule”

Every time you write, draw, photograph, or sculpt, you are creating a copyright work.  In New Zealand, this copyright is automatic and free, with no need to register – you only need to keep good records of your own creative process.

The owner of copyright in a work is the only one who is allowed to copy (or authorise others to copy) that work.  But how do you know whether something is a copy?

This is where the myth comes in – some people believe it is alright to copy something as long as you “change it by 10%”.  However, this has no connection with any legal test.  If you follow the “10% rule”, you should expect trouble (and no one wants a “cease and desist” letter).

The legal test for whether copyright has been infringed by a “copy” has several stages.  In this context, the two most relevant questions are:

  • Is the part of the work that has been copied a “substantial part” of the original copyright work?
  • Is the “copy” objectively similar to the original copyright work?

The first question relates to how important a part of the original copyright work the copied element it.  It might be only a single line in the words of an entire song, but if it is the most important line, it might be a “substantial part”.

The second question is whether the copy is similar to the original.  It does not matter what “percentage” the work has been changed, what matters is whether it resembles the original.  For example, does one floral wallpaper look like another, does the chord progression of one piece of music call to mind the other?

The best way to avoid infringing copyright is to follow an independent creation process.  Where this is not possible, you may be able to ask permission from the original copyright owner.

When you want to create a true “derivative work”, but avoid infringement, it is best to remember that the aim is to produce something that is not objectively similar to any substantial part of the original.

Instead of a “10% rule”, my summary of the case law is: a copy is a copy if it looks like a copy.


This article is part of a series of short items by our Intellectual Property specialist Virginia Nichols.  This is general information, not legal advice.  Contact us for specific tailored advice relating to your situation.