A proposed date cannot guarantee the missing qualification evidence will be accepted or available.
Plan around the actual record
Identify the outstanding confirmation and the employer’s flexibility. Do not describe the evidence as complete merely to preserve a booking.
The two long items usually sit outside the employer's control: a provincial regulator or registrar issuing a letter of standing, and a credential evaluation for a degree earned outside Canada or the United States. A Canadian citizen applying in person pays the border charge; an employer that prefers a petition pays the filing fee, with premium processing available at additional cost where a start date is tight. Because the employer's offer will be conditional on licensure, this is the item that most often moves a planned start date, and it should be begun as soon as the board permits rather than after an immigration question is settled. An updated employer letter, a current licence and any change in the role all take time to assemble, and a lapse in the licence or a gap in the employment record is much harder to remedy close to the deadline. A revised duty description waits on an employer's internal approvals; a registration confirmation waits on a regulator's queue; and where a petition route is used, processing waits on nobody in the room.