Definition of 'SEC Form 15' A filing with the Securities and Exchange Commission (SEC), also known as the Certification and Notice of Termination of Registration. It is used by publicly traded companies to revoke the registration of their securities. SEC Form 15 may also be used to notify the SEC and investors of a company's intent to cease filing various required forms because their securities no longer fall under certain filing requirements. Investopedia Says Investopedia explains 'SEC Form 15' When a company files an SEC Form 15, it usually means one of two things. It may mean that a company is ceasing to exist in a publicly-traded form, either returning to privately-held status or going out of business altogether. Alternatively, it may mean that a company is simply canceling a certain class of securities, replacing them with another class.