What is an incontestability affidavit?

An incontestability affidavit (also known as a Section 15 affidavit) relates to trademarks that have been federally registered pursuant to the Lanham Act. Specifically, it is a sworn statement which the trademark owner can file after five years of continuous use of the mark. While an incontestability affidavit does not have to be filed, it is advantageous to do so because it will allow the Patent and Trademark Office to deem the registered trademark incontestable, which strengthens the mark and its owner’s ability to protect it.