You may need copyright permission even if you are using just part of something, if the part is an important part of the work. In copyright law, this is referred to as a “substantial part”, but the part used need not be a large part.

Whether or not a part is sufficiently important to require permission is one of the most difficult issues in copyright law, because it depends on the circumstances of each case. There is no specific proportion or percentage. The quality of the part used is more important than its quantity; the skill and effort used to create the part you want to use is more important than how big it is, or what proportion it is. For example, Rudyard Kipling successfully sued for copyright infringement when one verse – 4 lines – of his 32 line poem "If" was used in an advertisement for Sanatogen pills, “a reviver of nerve power”.

It is also important to note that the purpose of the use may also be relevant – particularly if the use would compete with the copyright owner’s work.

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• Quotes & extracts
• When you need copyright permission