There is no requirement that an application for extension be sent to CItizenship and Immigration Canada at least 30 days before the expiry of status. An application can be made at any time up to the expiry of status. While waiting for the extension document the person enjoys "implied status." However, employers often lack an understanding of this concept. It is therefore advisable to apply for work permit extensions well in advance of expiry. The alternative is for counsel to explain the concept of implied status by way of a letter to the employer.