Begin with the licensing board, since its processing and meeting schedule usually determines the earliest lawful start and is the part nobody can accelerate. The immigration step can often be completed relatively quickly once the qualification documents and the employer's letter exist, and it should be scheduled behind the licence.
Let the slowest authority set the date
Ask the board two questions in the first week: how long verification and processing currently take for an applicant with an Ontario degree, and on what dates decisions are made. Put those on the calendar and count forward, then tell the employer what the earliest realistic start actually is. Practices that are short-staffed will press for something sooner, and the honest answer is that a veterinarian cannot practise without the licence regardless of immigration status. Use the interval productively: complete the credential verification, prepare the immigration documents so they are ready when the licence issues, and settle the arrangements for the Ontario practice. Do not resign, sell or move a household until both permissions are actually in hand.
Hypothetical example: a Tyendinaga forester is needed for a wildfire-recovery project that begins after a narrow seasonal window. The employer should work backward from the first lawful workday, then identify the slowest record: degree verification, licensing confirmation, or a corrected offer letter. A rushed file fails when dates conflict or duties are improvised. Keep a dated checklist and postpone travel until the evidence supports the role actually offered. The resulting sequence gives the employer a defensible start date and gives the professional time to correct a missing record.